Choose the best answer:
It’s good to have someone __________ you when you are visiting a new place.

 

Mark the letter A, B, C, or D on your answer sheet to indicate the undelined part that needs correction in each of the following questions:
In the course of its history, human inventions have dramatically increased the average amount of energy available for use per person. Primitive peoples in cold regions burned wood and animal dung to heat their caves, cook food, and drive off animals by fire. The first step toward the developing of more efficient fuels was taken when people discovered that they could use vegetable oils and animal fats in lieu of gathered or cut wood. Charcoal gave off more intensive heat than wood and was more easily obtainable than organic fats. The Greeks first began to use coal for metal smelting in the 4th century, but it did not come into extensive use until the Industrial Revolution.
In the 1700s, at the beginning of the Industrial Revolution, most energy used in the United States and other nations undergoing industrialization was obtained from perpetual and renewable sources, such as wood, water streams, domesticated animal labor, and wind. These were predominantly locally available supplies. By mid-1800s, 91 percent of all commercial energy consumed in the United States and European countries was obtained from wood. However, at he beginning of the 20th century, coal became a major energy source and replaced wood in industrializing countries. Although in most regions and climate zones wood was more readily accessible than coal, the latter represents a more concentrated source of energy. In 1910, natural gas and oil firmly replaced coal as the main source of fuel because they are lighter and, therefore, cheaper to transport. They burned more cleanly than coal and polluted less. Unlike coal, oil could be refined to manufacture liquid fuels for vehicles, a very important consideration in the early 1900s, when the automobile arrived on the scene.
By 1984, non-renewable fossil fuels, such as oil, coal, and natural gas, provided over 82 percent of the commercial and industrial energy used in the world. Small amounts of energy were derived from nuclear fission, and the remaining 16 percent came from burning direct perpetual and renewable fuels, such as biomass. Between 1700 and 1986, a large number of countries shifted from the use of energy from local sources to a centralized generation of hydropower and solar energy converted to electricity. The energy derived from non-renewable fossil fuels has been increasingly produced in one location and transported to another, as is the case with most automobile fuels. In countries with private, rather than public transportation, the age of non-renewable fuels has created a dependency on a finite resource that will have to be replaced.
Alternative fuel sources are numerous, and shale oil and hydrocarbons are just two examples. The extraction of shale oil from large deposits in Asian and European regions has proven to be labor consuming and costly. The resulting product is sulfur-and nitrogen-rich, and large scale extractions are presently prohibitive. Similarly, the extraction of hydrocarbons from tar sands in Alberta and Utah is complex. Semi-solid hydrocarbons cannot be easily separated from the sandstone and limestone that carry them, and modern technology is not sufficiently versatile for a large-scale removal of the material. However, both sources of fuel may eventually be needed as petroleum prices continue to rise and limitations in fossil fuel availability make alternative deposits more attractive.

What is the main topic of the passage?

Mark the letter A, B, C, or D on your answer sheet to indicate the undelined part that needs correction in each of the following questions:
These days, most people in Britain and the US do not wear very formal clothes. But sometimes it is important to wear the right thing.
Many British people don't think about clothes very much. They just like to be comfortable. When they go out to enjoy themselves, they can wear almost anything. At theatres, cinemas and concerts you can put on what you like from elegant suits and dresses to jeans and sweaters. Anything goes, as long as you look clean and tidy.

But in Britain, as well as in the US, men in offices usually wear suits and ties, and women wear dresses or skirts (not trousers). Doctors, lawyers and business people wear quite formal clothes. And in some hotels and restaurants men have to wear ties and women wear smart dresses.
In many years, Americans are more relaxed than British people, but they are more careful with their clothes. At home, or on holiday, most Americans wear informal or sporty clothes. But when they go out in the evening, they like to look elegant. In good hotels and restaurants, men have to wear jackets and ties, and women wear pretty clothes and smart hairstyles.
It is difficult to say exactly what people wear informal or formal in Britain and the US, because everyone is different. If you are not sure what to wear, watch what other people do and then do the same. You'll feel more relaxed if you don't look too different from everyone else.

If you are in a foreign country, the best way the writer suggests to you is to wear 

Choose the best answer:
You can use the ___________ control to adjust the air-conditioner.

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Every summer, when the results of university entrance exam come out, many newspaper stories are published about students who are top-scorers across the country. Most portray students as hard-working, studious, smart and, generally, from low-income families. They are often considered heroes or heroines by their families, communes, villages and communities. And they symbolise the efforts made to lift them, and their relatives, out of poverty. The students are often too poor to attend any extra-classes, which make their achievements more illustrious and more newsworthy. While everyone should applaud the students for their admirable efforts, putting too much emphasis on success generates some difficult questions. If other students look up to them as models, of course it’s great. However, in a way, it contributes to society’s attitude that getting into university is the only way to succeed. For those who fail, their lives are over. It should be noted that about 1.3 million high school students take part in the annual university entrance exams and only about 300,000 of them pass. What’s about the hundreds of thousands who fail? Should we demand more stories about those who fail the exam but succeed in life or about those who quit university education at some level and do something else unconventional? “I personally think that it’s not about you scoring top in an entrance exam or get even into Harvard. It’s about what you do for the rest of your life,” said Tran Nguyen Le Van, 29. He is the founder of a website, vexere.com, that passengers can use to book bus tickets online and receive tickets via SMS. His business also arranges online tickets via mobile phones and email. Van dropped out of his MBA at the Thunderbird School of Global Management in Arizona in the United States. His story has caught the attention of many newspapers and he believes more coverage should be given to the youngsters who can be role-models in the start-up community. Getting into university, even with honours, is just the beginning. "We applaud them and their efforts and obviously that can give them motivation to do better in life. However, success requires more than just scores," Van said. Van once told a newspaper that his inspiration also came from among the world’s most famous drop-outs, such as Mark Zuckerberg of Facebook or Bill Gates who also dropped out of Harvard University. Alarming statistics about unemployment continues to plague us. As many as 162,000 people with some kind of degree cannot find work, according to Labour Ministry’s statistics this month. An emphasis on getting into university does not inspire students who want to try alternative options. At the same time, the Ministry of Education and Training is still pondering on how to reform our exam system, which emphasises theories, but offers little to develop critical thinking or practice. Vu Thi Phuong Anh, former head of the Centre for Education Testing and Quality Assessment at Viet Nam National University in HCM City said the media should also monitor student successes after graduation. She agreed there were many success stories about young people, but added that it was imbalanced if students taking unconventional paths were not also encouraged. Viet Nam is, more than ever, in desperate need of those who think outside the box. Time for us to recognise talent, no matter where it comes from or how.
3. The word “unconventional” in paragraph 2 could best be replaced by ____________

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Generation gap refers to a vast difference in cultural norms between a younger generation and their elders. It’s a distressing thing for the phenomenon (1) ____ occurs around the world. The (2) ____ of communication, different views on certain problems and different attitudes towards life may cause the generation gap or even widen it. First, one of the major factors for this misunderstanding between two generations is that parents and children lack communication. Young people (3) ____ reveal their feelings to their parents, and often complain that their parents are out of (4) ____ with modern days, that they are dominant, that they do not trust their children to deal with crises, and that they talk too much about certain problems. So when young people meet some problems, they would rather (5) ____ to their classmates or their friends for help. The lack of communication widens the generation gap Another factor is that parents and their children see almost everything from different (6) ____. Take choosing career as an example. Parents generally believe it is their responsibility to plan the career for their children. Some hope their children will (7) ____ professions that will bring them greatest prestige and economic benefits. Some hope children will have a stable job with a regular income. But the youth may think they should be free to (8) ____ their own decisions as to their future career. Young people explain that true success is not a matter of money or position, instead, it is a matter of self-fulfillment. Finally, with the change of the world over decades, the attitude of the young has altered too. There are differences in (9) ____ matters as musical tastes, fashions, drug use, sex and politics between the young people and their elders. Nowadays long hair on young males is viewed as fashion by the young, but it is frequently considered a shocking act of rebellion against (10) ____ norms by parents

Rewrite the sentence:
mountain/ amazed/ Are/ seeing/ at/ the/ you?

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Clara Barton became known as “The Angel of the Battlefield” during the American Civial War. Born in Oxford, Massachusetts in 1821, Clara Barton’s interest in helping soldiers on the battlefield began when she was told army stories from her father. Another event that influenced her decision to help soldiers was an accident her brother had. His injuries were cared for by Barton for 2 years. At the time, she was only 11 years old. Barton began teaching school at the age of 15. She taught for 18 years before she moved to Washington, D.C. in 1854.
The civil war broke out 6 years later. Immediately, Barton started was service by helping the soldiers with their needs. At the battle of Bull Run, Clara Barton received permission from the government to take care of the sick and hurt. Barton did this with great empathy and kindness. She acknowledged each soldier as a person. Her endurance and courage on the

battlefield were admired by many. When the war ended in 1865, she used 4 years of her life to assist the government in searching for soldiers who were missing during the war.
The search for missing soldiers and years of hard work made her feeble physically. In 1869, her doctors recommended a trip to Europe for a rest. While she was on vacation, she became involved with the International Red Cross, an organization set up by the Geneva Convention in 1864. Clara Barton realized that the red Cross would be a big help to the United States. After she returned to the United States, she worked very hard to create an American red Cross. She talked to government leaders and let American people know about the Red Cross. In 1881, the Notional Society of the Red Cross was finally established with its headquarters in Washington, D.C. Clara Barton managed its activities for 23 years.
Barton never let her age stop her from helping people. At the age of 79, she helped flood victims in Galveston, Texas. Barton finally resigned from the Red Cross in 1904. She was 92 years old and had truly earned her titled “The Angel of the Battlefield”.

According to paragraph 1, which of the following is true of the young Clara Barton?

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For many years, scientists have speculated that the cataclysmic impact of an asteroid with the earth was responsible for the demise of the dinosaurs approximately 65 million years ago. Previous discoveries and results have hinted that an asteroid two kilometers in diameter struck the Yucatan peninsula in Eastern Mexico. This impact, stronger than one thousand nuclear explosions, is speculated to have cast a cloud of dust and debris into the atmosphere, covering the entire surface of the earth and blocking out the sun and consequently lowering the surface temperature of the earth. With such a radical change in the earth's environment, scientists believe that over 99% of all animal and plant species were eradicated. Only after millions of years did plants and animals even begin to recover and develop into forms that were better adapted to survive changes in their environment. But, the reign of the dinosaurs had ended and the age of mammals had begun. The crucial link that has held this theory together has been the element iridium. Iridium is not commonly found on either the surface of the earth or inside the crust. It is more commonly found in asteroids or meteorites throughout the solar system. Scientists have hypothesized that after the asteroid impacted the Earth, an even layer of iridium sediment settled over the globe and eventually became part of its surface. The theory, of course, has depended on the discovery of such an existing layer of iridium. Unfortunately, scientists have never been able to offer absolute proof that this asteroid impact ever occurred. Recently, however, a discovery may go a long way toward validating these scientists 'theories. In 1996, a team of marine biologists excavated samples of rock from the Atlantic Ocean just off the cost of Bermuda. Found thousands of meters below the sea, these samples contain iridium similar to those found in the Yucatan peninsula thousands of kilometers away. At first, scientists were skeptical whether the samples were from the same time period. But since carbon dating placed them to 65 million years ago, their doubts were quickly alleviated. Since then many of the other theories for the demise of the dinosaur have been finally laid to rest.
9. According to the passage, the iridium found beneath the ocean floor near Bermuda: 

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When living and working in another country, there are numerous things to consider  apart from the more obvious ones of climate, language, religion, currency, etc. Some important considerations are less obvious. For example, do you have a pet or do you enjoy a hobby such as horse riding? Your animal or hobby may be perceived in a completely different light in another culture so it’s important to consider the significance given to specific animals in different parts of the world and general perceptions towards them.  One example which is often mentioned in popular press is the case of dogs. In some cultures, like the US or UK, dogs are loved and considered a great pet to have at home and with the family. In other cultures, such as those where Islam is the majority religion, dogs may be perceived as dirty or dangerous. Muslims’ treatment of dogs is still a matter of debate amongst Islamic scholars . While these animals are widely considered by many Western cultures to be ‘man’s best friend’, the Koran describes them as unhygienic. Muslims will therefore avoid touching a dog unless he can wash his hands immediately afterwards, and they will almost never keep a dog in their home.  In Iran, for instance, a cleric once denounced ‘the moral depravity’ of dog owners and even demanded their arrest. If you are an international assignee living and working in Saudi Arabia or another Arabic country, you should remember this when inviting Arab counterparts to your house in case you have a dog as a pet. This is just one example of how Islam and other cultural beliefs can impact on aspects of everyday life that someone else may not even question. A Middle Eastern man might be very surprised when going to Japan, for instance, and seeing dogs being dressed and pampered like humans and carried around in baby prams!  Dogs are not the only animals which are perceived quite differently from one culture to another. In India, for example, cows are sacred and are treated with the utmost respect. Conversely in Argentina, beef is a symbol of national pride because of its tradition and the high quality of its cuts. An Indian working in Argentina who has not done his research or participated in a cross cultural training programme such as Doing Business in Argentina may be surprised at his first welcome dinner with his Argentinean counterparts where a main dish of beef would be served.  It is therefore crucial to be aware of the specific values assigned to objects or animals in different cultures to avoid faux-pas or cultural misunderstandings, particularly when living and working in another culture. Learning how people value animals and other symbols around the world is one of the numerous cultural examples discussed in Communicaid’s intercultural training courses. Understanding how your international colleagues may perceive certain animals can help you ensure you aren’t insensitive and it may even provide you with a good topic for conversation. 
6. The author mentioned cows in paragraph 4 as an example of _________

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Women’s representation in government is stalled, and in some cases moving backward. Does that make a difference to the work of governing? Yes, according to decades of data from around the world. Women govern differently than men do in some important ways. They tend to be more collaborative and bipartisan. They push for far more policies meant to support women, children, social welfare and — when they’re in executive positions — national security. But these bills are also more likely to die, largely because of gender bias, research shows. Women in Congress sponsor and co-sponsor more bills than men do, and bring 9 percent more federal money to their districts, according to a study in the American Journal of Political Science. Those bills are more likely to benefit women and children or address issues like education, health and poverty. In Congress, for instance, women fought for women’s health coverage in the Affordable Care Act, sexual harassment rules in the military, the inclusion of women in medical trials, and child care vouchers in welfare overhaul. “All members of Congress have to follow their constituency, but because of their personal experiences either as women in the work force or as mothers, they might be inclined to legislate on some of these issues,” said Michele L. Swers, a professor of government at Georgetown University who studies gender and policy making.  In a new analysis of the 151,824 public bills introduced in the House between 1973 and 2014, to be published in print in Political Science Research and Methods, researchers found that women were significantly more likely than men to sponsor bills in areas like civil rights, health and education. Men were more likely to sponsor bills in agriculture, energy and macroeconomics. An analysis of floor speeches during the 106th Congress, by political scientists at the University of Iowa and Oklahoma State University, found that women spent more time talking about policy concerns like women’s health and family issues. Another study, of State of the State speechesfrom 2006 to 2008 published in State and Local Government Review, found that female governors devoted much more attention to social welfare issues than male governors did, even after controlling for political and situational factors. Women are less likely to vote for war or the death penalty. Women’s representation in legislatures is significantly correlated with the abolition of capital punishment, according to a study of 125 countries published in July by researchers at Sul Ross State University in Texas. A higher share of female legislators correlates with less military spending and less use of force in foreign policy, even after controlling for other explanations like partisanship, according to an analysis by researchers from Texas A&M University of data from 22 established democracies from 1970 to 2000. Yet when women are in executive positions, the opposite is true: They are more hawkish than men. The researchers said that could be in part because of a need to overcome stereotypes of women as weak. Margaret Thatcher, Golda Meir and Indira Gandhi, all of whom governed in conflicts, were described as governing like men.  
4. According to the passage, as a worker and a mother, women tried to address many issues, EXCEPT ____________

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Nuts could be the key to keeping slim, according to new research. Scientists from Harvard University and Harvard Medical School say that replacing and unhealthy snack with half a daily _____ (1) of nuts could slow weight gain in people as they get older. Walnuts ____________ (2) particular appeared to offer good results and were linked to a 15% lower risk of obesity. Researchers conducted a long-term study which followed 51,529 male health professionals aged 40 to 5, 121,700 nurses aged 35 to 55 and 16,686 nurses aged 24 to 44. Participants had their weight ____________ (3) every four years and were asked how often they had eaten nuts. They also had to report their exercise every two years. The findings, ___________________ (4) in the online journal BMJ Nutrition, Prevention and Health, showed that increasing nut consumption was associated with less risk of putting on two or more kilos over a four-year period. However, the researchers say the study is ________ (5) and therefore cannot establish a definite cause

Find mistake:
When he came, I watched a football match on TV.

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You’ll be able to purchase high-quality emotions online. Emotion-sharing experiences  are the latest fad in 2045. Imagine your friend at Glastonbury can post a photo on Instagram and with it comes bundled a faint twinkling of what she was feeling right there in that moment, so you too can share emotionally in her social experience.  Recently, techniques for direct brain stimulation, like opt genetics, have made it possible to not only read but also write information into single neurons. At the moment data transfer rates are still very slow, the best we can do is a few bits per second, but this could well increase to kilobits or maybe reach broadband speeds by 2045. This means the range of human perception could expand beyond its current design limitations. One could foresee a new and extraordinary world where there is a virtual marketplace for trading high quality emotions – where artists looking for a particularly high strength brew of melancholy, or actors needing to channel regret or compassion for their next play, could purchase emotions online.  Our cities will be made from living, dynamic materials that respond to the environment. In 30 years, tall buildings made of glass and twisted steel will be seen as relics from a bygone era, in the same way we think now of 1970s concrete tower blocks: ugly, outdated and unfit for contemporary purpose. The urban environment of 2045 blends architecture with living materials that are mouldable, adaptable, responsive and disposable.  Entirely new synthetic life forms, or biological machines, made of engineered living cells from bacteria, fungi and algae will grow and evolve with the changing needs of a building’s inhabitants. They breathe in pollutants, clean wastewater, and use sunlight to make useful chemicals, energy, heat and vibrant vertical gardens. We will start to see a convergence between biology and technology, to the point where there is no longer a perceptible difference between the two. Today, synthetic biology labs are looking at the full diversity of what nature has to offer and using this to mix, match and edit genomes to design synthetic life forms. Right now, this field is just getting started and the science of synthetic biology is going to be tougher than most will admit.  We will use invisibility cloaks to “disappear” ugly objects. Invisibility has forever been a tantalizing prospect. The key to cloaking lies in the way the electromagnetic spectrum  (including visible light) interacts with objects. The human eye picks up electromagnetic radiation that falls and scatters from objects and we perceive this as light. In recent decades, scientists figured out using mathematics that it might just be possible to imagine a new class of artificial materials made of intricate tiny features with light bending properties. They named them metamaterials.  Using nanotechnology engineering, scientists have since shown cloaking actually works – in principle at least, for a narrow range of colours and only from certain viewing angles. The future applications of cloaking are highly uncertain and will likely be determined by the fads and social contagion of the time. They may be used in everything from novelty gimmicks to making unsightly construction sites and power stations seemingly ‘disappear’.   
1. Which of the following is the main idea of the passage?

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Although the “lie detectors” are being used by governments, police departments, and businesses that all want guaranteed ways of detecting the truth, the results are not always accurate. Lie detectors are properly called emotion detectors, for their aim is to measure bodily changes that contradict what a person says. The polygraph machine records changes in heart rate, breathing, blood pressure, and the electrical activity of the skin (galvanic skin response, or GSR). In the first part of the polygraph test, you are electronically connected to the machine and asked a few neutral questions (“What is your name?”, “Where do you live?”). Your physical reactions serve as the standard (baseline) for evaluating what comes next. Then you are asked a few critical questions among the neutral ones (“When did you rob the bank?”). The assumption is that if you are guilty, your body will reveal the truth, even if you try to deny it. Your heart rate, respiration, and GSR will change abruptly as you respond to the incriminating questions. That is the theory; but psychologists have found that lie detectors are simply not reliable. Since most physical changes are the same across all emotions, machines cannot tell whether you are feeling guilty, angry, nervous, thrilled, or revved up form an exciting day. Innocent people may be tense and nervous about the whole procedure. They may react physiologically to a certain word (“bank”) not because they robbed it, but because they recently bounced a check. In either case the machine will record a “lie”. The reverse mistake is also common. Some practiced liars can lie without flinching, and others learn to beat the machine by tensing muscles or thinking about an exciting experience during neutral questions
7. This passage was probably written by a specialist in _____

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Ask about “the population problem” to people of a certain age, and the first and perhaps only thing that comes to mind is the “population bomb” or “population explosion.” And they would be right - for their time. In the second half of the 20th century, rapid population growth - especially but not exclusively in the developing countries - created unprecedented increases in the number of people on the earth. And this growth was accompanied by crowding, malnutrition, disease, and poverty. Indeed, for many Americans, the coming “population explosion” was, along with the Cold War, the most unsettling fact about our world. But “population problems” have been part of American discourse for over 100 years. In the 1930s and 1940s, for instance, many observers feared that depopulation due to plummeting birth rates would cause chronic economic depression as the numbers of U.S. consumers and workers declined. In the 1920s, the U.S. “population problem” was rapid urbanization, reflected in a 1920 census count showing that for the first time more than onehalf the population lived in urban areas. Rural incumbents in the House of Representatives, fearing they would be voted out of office by their new urban constituents, succeeded in blocking reapportionment of the House’s seats on the basis of the census counts as mandated by the U.S. Constitution. The century’s first “population problem” was mass xenophobia about immigration. Beginning in 1880, wave after wave of European immigrants was creating congestion and social change at an unprecedented rate. In response to widespread anxiety and anger, Congress in 1924 passed the country’s most restrictive immigration legislation ever. Each problem was based in hard numbers. Each generated private emotions and public fears. Each suffered exaggeration and manipulation. And each commanded the attention of opinion leaders and elected officials.  
1. Which best serves as the title for the passage?

A pilot cannot fly by sight alone. In many conditions, such as flying at night and landing in dense fog, a pilot must use radar, an alternative way of navigating. Since human eyes are not very good at determining speeds of approaching objects, radar can show a pilot how fast nearby planes are moving. The basic principle of radar is exemplified by what happens when one shouts in a cave. The echo of the sounds against the walls helps a person determine the size of the cave. With radar, however, the waves are radio waves instead of sound waves. Radio waves travel at the speed of light, about 300,000 kilometres in one second. A radar set sends out a short burst of radio waves. Then it receives the echoes produced when the waves bounce off objects. By determining the tune it takes for the echoes to return to the radar set, a trained technician can determine the distance between the radar set and other objects. The word "radar" in fact gets its name from the term "radio detection and ranging". "Ranging" is the term for detection of the distance between an object and the radar set. Besides being of critical importance to pilots radar is essential for air traffic control tracking ships at sea, and for tracking weather Systems and storms.

What is the main topic of this passage?

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Why has Holmes continued to (1) _________________ generation after generation when other fictional detectives of the Victorian period are forgotten? One can break the answers down into a mix of elements. But first it will be useful to summarize the life of Holmes’s (2)____________. Doyle was born in Edinburgh in 1859, one of nine children of an alcoholic Irish artist who was consigned, in later life, to a lunatic asylum. Young Arthur Doyle was educated at the fee-paying Jesuit college, Stony Hurst. (3)___________ 16 he spent a year in Austria before enrolling at Edinburgh University’s medical school. In 1880 he spent seven months in the Arctic as ship’s doctor on a whaler. The following year he graduated with a (4)__________ degree, and made another trip to Africa before setting up, less adventurously, in medical practice near Portsmouth, in July 1882. His income had reached £300 a year by 1885, enabling him to marry the sister of one of his patients. Doyle had long written on the side and in 1886 he played around with stories (5)____________ on an ‘amateur private detec-tive’, called ‘J. Sherrinford Holmes’. The outcome was the Sherlock Holmes novella, A Study in Scarlet (1887). No top-drawer publisher would take it and it was eventually serialized as a Christmas giveaway in a magazine and then as what was called a ‘shilling shocker’ – pulp fiction for the masses

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Light-emitting diodes (LEDs) are now considered the future of lighting due to a lower energy requirement to run, a lower monthly price tag, and a longer life than traditional incandescent light bulbs. Nick Holonyak, an American scientist at General Electric, accidently invented the red LED light while trying to create a laser in the early 1960s. As with other inventors, the principle that some semiconductors glowed when an electric current was applied had been known since the early 1900s, but Holonyak was the first to patent it for use as a light fixture. Within a few years, yellow and green LEDs were added to the mix and used in several applications including indicator lights, calculator displays, and traffic lights, according to the DOE. The blue LED was created in the early 1990s by Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura, a group of Japanese and American scientists, and for which they won the 2014 Nobel Prize in Physics. The blue LED allowed scientists to create white LED light bulbs by coating the diodes with phosphor Today, lighting choices have expanded and people can choose different types of light bulbs, including compact fluorescent (CFL) bulbs work by heating a gas that produces ultraviolet light and LED bulbs. Several lighting companies are pushing the boundaries of what light bulbs can do, including Phillips and Stack. Phillips is one of several companies that have created wireless light bulbs that can be controlled via smartphone app. The Phillips Hue uses LED technology that can quickly be turned on or off or dimmed by a flick on a smart phone screen and can also be programmed. The higher-end Hue light bulbs can even be set to a large range of colors (only about sixteen million) and synced with music, movies, and video games. Stack, begun by engineers from Tesla and NASA, developed a smart light bulb using LED technology with a wide range of functions. It can automatically sense the ambient lighting and adjust as needed, it turns off and on via motion sensor when someone enters the room, can be used as a wake up alert, and even adjusts color throughout the day to fit with human’s natural circadian cycles and patterns of natural light. The light bulbs also have a built-in learning program that adapts to inputs given by residents over time. And all of these functions can be programmed or monitored from any smart phone or tablet. It is estimated that Stack smart light bulbs can use about sixty percent less energy than a typical LED light bulb and lasts between twenty and thirty thousand hours depending on the model . These light bulbs are compatible (or soon will be) with many of the options for turning an entire home into a smart home including usage with Amazon Alexa, Google Home, and Apple HomeKit.
2. What does the word “principle” in paragraph 2 mostly mean?

Mark the letter A, B, C, or D on your answer sheet to indicate the undelined part that needs correction in each of the following questions:
In the course of its history, human inventions have dramatically increased the average amount of energy available for use per person. Primitive peoples in cold regions burned wood and animal dung to heat their caves, cook food, and drive off animals by fire. The first step toward the developing of more efficient fuels was taken when people discovered that they could use vegetable oils and animal fats in lieu of gathered or cut wood. Charcoal gave off more intensive heat than wood and was more easily obtainable than organic fats. The Greeks first began to use coal for metal smelting in the 4th century, but it did not come into extensive use until the Industrial Revolution.
In the 1700s, at the beginning of the Industrial Revolution, most energy used in the United States and other nations undergoing industrialization was obtained from perpetual and renewable sources, such as wood, water streams, domesticated animal labor, and wind. These were predominantly locally available supplies. By mid-1800s, 91 percent of all commercial energy consumed in the United States and European countries was obtained from wood. However, at he beginning of the 20th century, coal became a major energy source and replaced wood in industrializing countries. Although in most regions and climate zones wood was more readily accessible than coal, the latter represents a more concentrated source of energy. In 1910, natural gas and oil firmly replaced coal as the main source of fuel because they are lighter and, therefore, cheaper to transport. They burned more cleanly than coal and polluted less. Unlike coal, oil could be refined to manufacture liquid fuels for vehicles, a very important consideration in the early 1900s, when the automobile arrived on the scene.
By 1984, non-renewable fossil fuels, such as oil, coal, and natural gas, provided over 82 percent of the commercial and industrial energy used in the world. Small amounts of energy were derived from nuclear fission, and the remaining 16 percent came from burning direct perpetual and renewable fuels, such as biomass. Between 1700 and 1986, a large number of countries shifted from the use of energy from local sources to a centralized generation of hydropower and solar energy converted to electricity. The energy derived from non-renewable fossil fuels has been increasingly produced in one location and transported to another, as is the case with most automobile fuels. In countries with private, rather than public transportation, the age of non-renewable fuels has created a dependency on a finite resource that will have to be replaced.
Alternative fuel sources are numerous, and shale oil and hydrocarbons are just two examples. The extraction of shale oil from large deposits in Asian and European regions has proven to be labor consuming and costly. The resulting product is sulfur-and nitrogen-rich, and large scale extractions are presently prohibitive. Similarly, the extraction of hydrocarbons from tar sands in Alberta and Utah is complex. Semi-solid hydrocarbons cannot be easily separated from the sandstone and limestone that carry them, and modern technology is not sufficiently versatile for a large-scale removal of the material. However, both sources of fuel may eventually be needed as petroleum prices continue to rise and limitations in fossil fuel availability make alternative deposits more attractive.

It can be inferred from the passage that in the early 20th centurgy, energy was obtained primarily from

Find synonym:
In order to stay healthy, make sure you have a balanced intake of vitamins and minerals.