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Vitamins, taken in tiny doses, are a major group of organic compounds that regulate the mechanisms by which the body converts food into energy. They should not be confused with minerals, which are inorganic in their makeup. Although in general the naming of vitamins followed the alphabetical order of their identification, the nomenclature of individual substances may appear to be somewhat random and disorganized. Among the 13 vitamins known today, five are produced in the body. Because the body produces sufficient quantities of some but not all vitamins, they must be supplemented in the daily diet. Although each vitamin has its specific designation and cannot be replaced by another compound, a lack of one vitamin can interfere with the processing of another. When a lack of even one vitamin in a diet is continual, a vitamin deficiency may result.
The best way for an individual to ensure a necessary supply of vitamins is to maintain a balanced diet that includes a variety of foods and provides adequate quantities of all the compounds. Some people take vitamin supplements, predominantly in the form of tablets. The vitamins in such supplements are equivalent to those in food, but an adult who maintains a balanced diet does not need a daily supplement. The ingestion of supplements is recommended only to correct an existing deficiency due to unbalanced diet, to provide vitamins known to be lacking in a restricted diet, or to act as a therapeutic measure in medical treatment. Specifically, caution must be exercised with fat-soluble substances, such as vitamins A and D, because, taken in gigantic doses, they may present a serious health hazard over a period of time.

How many vitamins must be derived from nourishment?

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Theresa May, the second female Britain’s prime minister following Margaret Thatcher, revealed in 2013 that she had been given a diagnosis of Type 1 diabetes, a condition that requires daily insulin injections. Asked later how she felt about the diagnosis, she said her approach to it was the same as toward everything in her life: “Just get on and deal with it.” That kind of steeliness brought her to center stage in the aftermath of Britain’s vote to leave the European Union and the feuding that erupted in the Conservative Party over who would succeed David Cameron.
Ms” May, 59 years old, is the country’s longest-serving home secretary in half a century, with a reputation for seriousness, hard work and above all, determination. She is one of a growing number of women in traditionally male-dominated British politics rising to the upper position of leadership.
Bom in 1956, Ms. May grew up mainly in Oxford shire, an only child who was first drawn to the Conservative Party at age 12. As a conscientious student, she never rebelled against her religious upbringing and remains a regular churchgoer. Tellingly, her sports hero was Geoffrey Boycott, a solid, stubborn cricketer who specialized in playing the long game.
Like many other Britain’s prime minister including Tony Blair, Sir Robert Peel and Margaret Thatcher, she won a place at Oxford. But while almost every other political leader got there by way of Eton College and joined Oxford’s hedonistic Bullingdon Club, she attended a state secondary school and had a more sedate university career. After unsuccessful attempts to be elected to the House of Commons in 1992 and 1994, she finally became an MP in 1997 general election.
May is known for a love of fashion and in particular distinctive shoes. She even wore leopard-print shoes to her final Cabinet meeting as Home Secretary in early 2016. However, she has been quite critical of the media focusing on her fashion instead of her achievement as a politician. May also describes cooking and walking as primary hobbies, and if someone is raising questions about why walking can be classified as a hobby, she elaborates in a column for Balance magazine, in which she wrote of her battle with diabetes.

Which of the following statements is NOT true?

Choose the word or phrase among A, B, C or D that best fits the blank space in the following passage:

"Before the 1960s, Singapore was essential a trading nation. Since (1)….. , it has developed a more (2)…. economy and has become an important financial, trade, and transportation center. Singapore has (3)….. banks, insurance, and finance companies, as (4) …..  as a stock exchange. Tourism is also important to the (5)…. of Singapore.
 There is (6)…. unemployment in Singapore. The country’s annual income per capita (per person) is one of the (7) …. in Asia. The government of Singapore plays a major role in the country’s economy. For example, it (8)….. what benefits, such as vacation time and sick leave, must be (9)….for workers by employers. It also operates an employment agency to help people find jobs, and it provides (10)…..  for retired workers."

6. There is (6)…. unemployment in Singapore. 

Iron production was revolutionized in the early eighteenth century when coke was first used instead of charcoal for refining iron ore. Previously the poor quality of the iron had restricted its use in architecture to items such as chains and tie bars for supporting arches, vaults, and walls. With the improvement in refining ore, it was now possible  to  make  cast-iron beams, columns, and girders. During the nineteenth century further advances were made, notably Bessemer’s process for converting iron into steel, which made the material more commercially viable.
Iron was rapidly adopted for the  construction  of  bridges,  because  its  strength was far greater  than that of stone or timber, but its use in the architecture of buildings developed more slowly. By 1800 a complete internal iron skeleton for buildings had been developed in industrial architecture replacing traditional timber beams, but it generally remained concealed. Apart from its low cost, the appeal of iron as a building material lay in its strength, its resistance to fire, and its potential to span vast areas. As a result, iron became increasingly popular as a structural material for more traditional styles of architecture during the nineteenth century, but it was invariably concealed.
Significantly, the use  of  exposed  iron  occurred  mainly  in  the  new  building types spawned by the Industrial Revolution: in factories, warehouses, commercial offices, exhibition hall, and railroad stations, where its  practical  advantages  far  outweighed  its  lack of status. Designers of the railroad stations of the new age explored the potential of iron, covering huge areas with spans that surpassed the great vaults of medieval churches and cathedrals. Paxton’s Crystal Palace, designed to house the Great Exhibition of 1851, covered an area of 1.848 feet by 408 feet in prefabricated units of glass set in iron frames. The Paris Exhibition of 1889 included both the widest span and the  greatest height achieved so far with the Halle Des Machines, spanning 362 feet, and the Eiffel Tower 1,000 feet high. However, these achievements were mocked by the artistic elite of Paris as expensive and ugly follies. Iron, despite its structural advantages, had little aesthetic status. The use of an exposed iron structure in the more traditional styles of architecture was slower to develop.

What does the passage mainly discuss?

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Our eyes and ears might be called transformers because they send the light and sound around us and turn them into electrical impulses that the brain can interpret. These electrical impulses that have been transformed by the eyes and ears reach the brain and are turned into massages that we can interpret. For the eye, the process begins as the eye admits light waves, bends them at the cornea and lens, and then focuses them on the retina. At the back of each eye, nerve fibers bundle together to form optic nerves, which join and then split into optic tracts. Some of the fibers cross so that part of the input from the right visual field goes into the left side of the brain, and vice versa. The process in the ear is carried out through sensory cells that are carried in fluid-filled canals and that are extremely sensitive to vibration. Sound that is transformed into electricity travels along nerve fibers in the auditory nerve. These fibers form a synapse with neurons that carry the massages to the auditory cortex on each side of the brain.

Which of the following is closest in meaning to the word “admits” in line 4?

The initial contact between American Indians and European settlers usually involved trade, whereby Indians acquired tools and firearms and the Europeans obtained furs. These initial events usually pitted Indian tribes against each other as they competed for the European trade and for the lands containing fur-producing animals. When the furs had been depleted, the Europeans began a campaign to obtain the lands the Indians occupied. The Indians often formed confederations and alliances to fight back the Europeans; however, the Indians’ involvement in the white people’s wars usually disrupted these confederations. Indians resisted the attempts by the whites to displace them. They fought defensive wars such as the Black Hawk War in 1832. Indian uprisings also occurred, like the Sioux uprising in the 1860s.
Despite the resistance of the Indians, the Europeans were destined to win the conflict. After Indian resistance was crushed, the whites legitimized the taking of Indian lands by proposing treaties, frequently offering gifts to Indian chiefs to get them sign the treaties. Once an Indian group had signed a treaty, the whites proceeded to remove them from their land. Often the Indians were forced west of the Mississippi into Indian Territory-land the whites considered uninhabitable. If only a few Indians remained after the conquest, they were often absorbed by local tribes or forced onto reservations.
No aspect of American history is more poignant than the accounts of the forced removal of Indians across the continent. As white settlers migrated farther west, Indians were forced to sign new treaties giving up the lands earlier treaties had promised them. Some Indian tribes, realizing the futility of resistance, accepted their fate and moved westward without force. The Winnebagos, who offered little resistance, were shifted from place to place between 1829 and 1866. About half of them perished during their perpetual sojourn. Other tribes, however, bitterly resisted. The Seminoles signed a treaty in 1832 but violently resisted removal. Hostilities broke out in 1835 and continued for seven years. The United States government lost nearly 1,500 men and spent over $50 million in its attempts to crush Seminole resistance. Most of Seminoles were eventually forced to Indian Territory. However, several hundred remained in the Florida Everglades, where their descendants live today.

The author makes the point that Indian Territory was ..............

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Welcome to the Netherlands, a tiny country that only extends, at its broadest, 312 km north to  south, and 264 km east to west - (1) ......... the land area increases slightly each year as a result of continuous land reclamation and drainage. With a lot of heart and much to offer, ‘Holland,’ as it is (2).......known to most of us abroad - a name stemming from its once most prominent provinces - has more  going  on  per  kilometer  than  most  countries,  and  more  English-speaking  natives.  You’ll  be impressed by its (3).....cities and charmed by its countryside and villages, full of contrasts. From the exciting variety on offer, you could choose a romantic canal boat tour in Amsterdam, a Royal Tour by coach in The Hague, or a hydrofoil tour around the biggest harbour in the world - Rotterdam. In season you could visit the dazzling bulb fields, enjoy a full day on a boat, or take a bike tour through the pancake-flat countryside spiced with windmills. The possibilities are countless and the nationwide tourist office is on hand to give you information and help you (4)...... reservations.  You’ll  have (5)........language problems here, as the Dutch are true linguists and English is spoken here almost universally.
(3)...........................

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Neil Armstrong started flying at an early age. He became interested in airplanes at the age of 2. At 15, he took flying lessons. He got a license to fly at 16. He learned how to fly before he learned how to drive a car. At university, he studied aeronautical engineering. This is the study of designing and making aircraft.
After Armstrong became an astronaut in 1962, he was trained for 4 years for the Apollo program. The Apollo mission was to put a man on the moon in ten years. On July 16, 1969, the Apollo 11 landed on the moon. Because Armstrong was the leader, he became the first man to step on the moon. He said, "This is one small step for a man, one giant leap for mankind." He and his fellow astronaut, Buzz Aldrin, walked on the moon for two and a half hours. They collected rocks and did some experiments.

The author's main purpose in paragraph 2 is     .

Choose the word or phrase among A, B, C or D that best fits the blank space in the following passage:

"Quite apart from the economic similarity between present-day automation and the mechanization which has been proceeding for centuries, it must also be stressed that even in the United States automation is by no means the only factor (1)….. people from existing jobs.
 The increasing number of unneeded workers in (2)…. years has been the result of much more simple and old-fashioned influences: farm labourers have been (3)…. out of work by bigger tractors, miners by the cheapness of oil, and railwaymen by better roads.
 It is quite wrong, therefore, to think of automation as some new monster whose arrival (4)…. the existence of employment in the same way that the arrival of myxomatosis threatened the existence of the rabbit. Automation is one (5)….. of technological change, which itself is only one of the several changes (changes in tastes, changes in social patterns, changes in organization) which (6)…. in certain jobs disappearing and certain skills ceasing to be required. And even in America, which has a level of technology and output per (7)…. much in (8)….. of Britain’s, there is no (9)…. that the (10)….  of change is actually speeding up.
 Nevertheless changes in the amount of labour needed to produce a certain output are proceeding fairly rapidly in America - and in other countries - and my proceed more rapidly in future. Indeed it is one of the main objects of economic policy."

2. The increasing number of unneeded workers in (2)…. years has been the result of much more simple and old-fashioned influences: 

Whales are the largest animals in the world, and the gentlest creatures we know. Although the whale is very huge, it is not hindered at all by its size when it is in the water. Whales have tails that end like flippers. With just a gentle flick, it can propel itself forward. The skin of a whale is so smooth that it does not create any friction that can slow the whale down. A whale’s breathing hole is located on the top of its head, so it can breathe without having to completely push its head out of the water. Whales are protected from the cold seawater by body fat that is called blubber.
Whales live in the ocean but, in terms of behaviours, they are more similar to humans than fish. They live in family groups and they even travel in groups when they have to migrate from cooler to warmer waters. The young stay with their parents for as long as fifteen years. Whales are known not to desert the ill or injured members; instead, they cradle them.
When whales are in danger, there are people who go to great lengths to help them. One such case occurred in 1988, when three young whales were trapped in the sea. It was close to winter and the sea had begun to freeze over. Whales are mammals that require oxygen from the air, so the frozen ice was a great danger to them. All they had then was a tiny hole in the ice for them to breathe through. Volunteers from all over soon turned up to help these creatures. They cut holes in the ice to provide more breathing holes for the whales. These holes would also serve as guides for the whales so that they could swim to warmer waters.

Which of the following best describes the main idea of this passage?

Choose the word or phrase among A, B, C or D that best fits the blank space in the following passage.

We won't have robot doctors for a long time, (1) ____ the human doctors we have now are beginning to learn on specialized artificial intelligence to help save time.

Google Deep Mind has just announced a partnership with University College London Hospital(UCLH) which will explore (2) ____ artificial intelligence to treat patients with head and neck cancers. The goal is to develop tools to automatically identify cancerous cells for radiology machines.

Currently, radiologists employ a manual process, called image (3) ____, to make CT and MRI scans and use them to create a map of the patient's anatomy with clear guidelines of where to direct the (4) ____.

Avoiding healthy areas of the head and neck requires that map to be extraordinarily detailed; typically it takes four hours to create. Google believes it can do the same job or better in one hour.

Deep Mind, Google's research arm, works primarily in deep learning, a form of artificial intelligence that learns to identify patterns from looking at large amount of data. In this case, DeepMind researchers will (5) ____ access to anonymized radiology scans from up to 700 former UCLH patients, and then feed them into (6) ____ that would process the scans to learn the visual difference between healthy and cancerous tissue.

The partnership will (7) ____ researchers to train their algorithms with highly-specialized, high- quality data, which theoretically will enable the algorithm to (8) ____ at a higher rate of success than if they had been using publicly available scans.

For those concerned about machines making health (9) ____ decisions, UCLH made it clear in a statement to the newspaper Guardian that clinicians will be in complete control of diagnoses and treatment.

DeepMind isn't the first care. Samsung Medison, the South Korean (10) ____ company's medical device arm, recently released an ultrasound machine that uses deep learning to quickly recommend whether breast tissue is cancerous or benign. The machine's algorithm was trained on 9,000 breast tissue scans, and is pending FDA approval in the US.

(1) ____

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The traditional definition of literacy is considered to be the ability to read and write, or the ability to use language to read, write, listen, and speak. In modern contexts, the word refers to reading 4 and writing at a level (1)......... for communication, or at a level that lets one understand and communicate ideas in a literate society so as to take (2)....... in that society. The United Nations Educational, Scientific and Cultural Organization (UNESCO) has drafted the following definition: “Literacy is the ability to identify, understand, interpret, create, communicate and compute, using printed and written materials associated with varying contexts. Literacy involves a continuum of learning to enable an individual to achieve his or her goals, to develop his, or her knowledge and potential, and to participate fully in the wider society.”
Many policy analysts consider literacy rates a crucial measure of a region’s human capital. This claim is made on the (3)........ that literate people can be trained less expensively than illiterate people, generally have a higher socio-economic status and enjoy better health and employment prospects. Policy makers also argue that literacy increases job opportunities and access to higher education. In Kerala, India, for example, female and child mortality rates declined (4)......... in the 1960s, when girls who were educated in the education reforms after 1948 began to raise families. Recent researchers, (5)........., argue that correlations such as, the one listed above may have more to do with the effect of schooling rather than literacy in general.
(2)..............................

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Puerto Rico, a Caribbean island rich in history and remarkable natural beauty, has a cuisine all its own. Immigration to the island has helped to shape its cuisine, with people from all over the world making various contributions to it. However, before the arrival of these immigrants, the island of Puerto Rico was already known as Borikén and was inhabited by the Taíno people. Taíno cuisine included such foods as rodents with sweet chili peppers, fresh shellfish, yams, and fish fried in corn oil.
Many aspects of Taíno cuisine continue today in Puerto Rican cooking, but it has been heavily influenced by the Spanish, who invaded Puerto Rico in 1508, and Africans, who were initially brought to Puerto Rico to work as slaves. (2)Taíno cooking styles were mixed with ideas brought by the Spanish and Africans to create new dishes. (3) Africans also added to the island’s food culture by introducing powerful, contrasting tastes in dishes like piñon–plantains layered in ground beef. In fact, much of the food Puerto Rico is now famous for—plantains, coffee, sugarcane, coconuts, and oranges—was actually imported by foreigners to the island. (4)
A common assumption many people make about Puerto Rican food is that it is very spicy. It’s true that chili peppers are popular; ajícaballero in particular is a very hot chili pepper that Puerto Ricans enjoy. However, milder tastes are popular too, such as sofrito. The 25 base of many Puerto Rican dishes, sofrito is a sauce made from chopped onions, garlic, green bell peppers, sweet chili peppers, oregano, cilantro, and a handful of other spices. It is fried in oil and then added to other dishes.

Look at the four numbers (1), (2), (3), and (4) in paragraph 2 that indicate where this sentence can be added to the passage. Where would the sentence fit best?

The Spanish extended food choices by bringing cattle, pigs, 15 goats, and sheep to the island.

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What makes it rain? Rain falls from clouds for the same reason anything falls to Earth. The Earth’s gravity pulls it. But every cloud is made of water droplets or ice crystals. Why doesn’t rain or snow fall constantly from all clouds? The droplets or ice crystals in clouds are exceedingly small. The effect of gravity on them is minute. Air currents move and lift droplets so that the net downward displacement is zero, even though the droplets are in constant motion.
Droplets and ice crystals behave somewhat like dust in the air made visible in a shaft of sunlight. To the casual observer, dust seems to act in a totally random fashion moving about chaotically without fixed direction. But in fact dust particles are much larger than water droplets and they finally fall. The cloud droplet of average size is only 1/2500 inch in diameter. It is so small that it would take sixteen hours to fall half a mile in perfectly still air, and it does not fall out of moving air at all. Only when the droplet grows to a diameter of 1/125 inch or larger can it fall from the cloud. The average raindrop contains a million times as much water as a tiny cloud droplet. The growth of a cloud droplet to a size large enough to fall out is the cause of rain and other forms of precipitation. This important growth process is called “coalescence”.

What is an example of precipitation?

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In the United States, friendship can be close, constant, intense, generous and real, yet fade away in a short time if circumstances change. Neither side feels hurt by this. Both may exchange Christmas greetings for a year or two, perhaps a few letters for a while - then no more. If the same two people meet again by chance, even years later, they pick up the friendship where they left off and are delighted.
In the United States, you can feel free to visit people's homes, share their holidays, or enjoy their lives without fear that they are taking on a lasting obligation. Do not hesitate to accept hospitality because you can’t give it in turn. No one will expect you to do so for they know you are far from home. Americans will enjoy welcoming you and be pleased if you accept their hospitality easily.
Once you arrived there, the welcome will be fun, warm, and real. Most visitors find themselves readily invited into many homes there. In some countries it is considered inhospitable to entertain at home, offering what is felt as only home cooked food, not doing something for your guests." It is felt that restaurant entertaining shows more respect and welcome. Or for other different reasons, such as crowded space, language difficulties, or family customs, outsiders are not invited into homes.
In the United States, both methods are used, but it is often considered friendlier to invite a person to one's home than to go to a public place, except in purely business relationship. So, if your host or hostess brings you home, do not feel that you are being shown inferior treatment.
Don't feel neglected if you do not find flowers awaiting you in your hotel room, either. Flowers are very expensive there; hotel delivery is uncertain; arrival times are delayed, changed or cancelled - so flowers are not customarily sent as a welcoming touch. Please do not feel unwanted! Outward signs vary in different lands; the inward welcome is what matters, and this will be real.A

In the United States, inviting guests to a family dinner is    than inviting them to a public place, except some situations.

Fill in each numbered blank with one suitable word or phrase.

In 1986 Vietnam (1)_____ a political and economic innovation campaign (Doi Moi) that introduced reforms intended to facilitate the transition from a centralized economy to a “socialist-oriented market economy”. Doi Moi combined government planning with free-market incentives. The program abolished agricultural (2) _____, removed price controls on agricultural goods, and enabled farmers to sell their goods in the marketplace. It encouraged the establishment of private businesses and foreign investment, including foreign-owned (3) _____.

By the late 1990s, the success of the business and agricultural (4) _____ ushered in under Doi Moi was evident. More than 30,000 private businesses had been (5) _____, and the economy was growing at an annual rate of more than 7 percent. From the early 1990s to 2005, poverty (6) _____ from about 50 percent to 29 percent of the population. However, progress varied geographically, with most prosperity concentrated in urban areas, (7) _____ in and around Ho Chi Minh City. In general, rural areas also made progress, as rural households (8) _____ in poverty declined from 66 percent of the total in 1993 to 36 percent in 2002. (9) _____ contrast, concentrations of poverty remained in (10) _____ rural areas, particularly the northwest, north-central coast, and central highlands. Government control of the economy and a nonconvertible currency have protected Vietnam from what could have been a more severe impact resulting from the East Asian financial crisis in 1997.

(1)_____

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In the United States and Canada, it is very important to (1)___________ a person directly in the eyes when you are having a conversation with him or her. If you look down or to the side when the other person is talking, that person will think that you are not interested in (2)___________ he or she is saying. This, (3) __________is not polite. If you look down or to the side when you are talking, it might seem that you are not honest.

However, people who are speaking will sometimes look away for a few seconds when they are thinking or (4)______________ to find the right word. But they always turn immediately back to look the listener directly in the eyes. These social "rules" are (5)___________ for two men, two women, a man and a woman, or an adult and a child.

(1)___________

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In the late 1960’s, many people in North America turned their attention to environmental problems and new steel-and-glass skyscrapers were widely criticized. Ecologists pointed out that a cluster of tall buildings in a city often overburdens public transportation and parking lot capacities.
Skyscrapers are also lavish consumers, and waster, of electric power. In one recent year, the addition of 17 million square feet of skyscraper office space in New York City raised the peak daily demand for electricity by 120,-000 kilowatts- enough to supply the entire city of Albany, New York, for a day.
Glass-walled skyscrapers can be especially wasteful. The heat loss (or gain) through a wall of half-inch plate glass is more than ten times that through a typical masonry wall filled with insulation board. To lessen the strain on heating and air- conditioning equipment, builders of skyscrapers have begun to use double glazed panels of glass, and reflective glasses coated with silver or gold mirror films that reduce glare as well as heat gain. However, mirror-walled skyscrapers raise the temperature of the surrounding air and affect neighboring buildings.
Skyscrapers put a severe strain on a city’s sanitation facilities, too. If fully occupied, the two World Trade Center towers in New York City would alone generate 2.25 million gallons of raw sewage each year-as much as a city the size of Stamford, Connecticut, which has a population of more than 109,000.
Skyscrapers also interfere with television reception, block bird flyways, and obstruct air traffic. In Boston, in the late 1960’s some people even feared that shadows from skyscrapers would kill the grass on Boston Common.
Still, people continue to build skyscrapers for all the reasons that they have always built them – personal ambition, civic pride, and the desire of owners to have the largest possible amount of rentable space.

The author raises issues that would most concern which of the following groups?

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The ocean bottom - a region nearly 2.5 times greater than the total land area of Earth - is a vast frontier that even today is largely unexplored and uncharted. Until about a century ago, the deep-ocean floor was completely inaccessible, hidden beneath waters averaging over 3,600 meters deep. Totally without light and subjected to intense pressures hundreds of times greater than at the Earth's surface, the deep-ocean bottom is a hostile environment to humans, in some ways as forbidding and remote as the void of outer space.
Although researchers have taken samples of deep-ocean rocks and sediments for over a century, the first detailed global investigation of the ocean bottom did not actually start until 1968, with the beginning ofthe National Science Foundation's Deep Sea Drilling Project (DSDP). Using techniques first developed for the offshore oil and gas industry, the DSDP's drill ship, the Glomar Challenger, was able to maintain a steady position on the ocean's surface and drill in very deep waters, extracting samples of sediments and rock from the ocean floor.
The Glomar Challenger completed 96 voyages in a 15-year research program that ended in November 1983. During this time, the vessel logged 600,000 kilometers and took almost 20,000 core samples of seabed sediments and rocks at 624 drilling sites around the world. The Glomar Challenger's core samples have allowed geologists to reconstruct what the planet looked like hundreds of millions of years ago and to calculate what it will probably look like millions of years in the future. Today, largely on the strength of evidence gathered during the Glomar Challenger's voyages, nearly all earth scientists agree on the theories of plate tectonics and continental drift that explain many of the geological processes that shape the Earth.
The cores of sediment drilled by the Glomar Challenger have also yielded information critical to understanding the world's past climates. Deep-ocean sediments provide a climatic record stretching back hundreds of millions of years, because they are largely isolated from the mechanical erosion and the intense chemical and biological activity that rapidly destroy much land-based evidence of past climates. This record has already provided insights into the patterns and causes of past climatic change - information that may be used to predict future climates.

The word “inaccessible” is closest in meaning to     .

In addition to the great ridges and volcanic chains, the oceans conceal another form of undersea mountains: the strange guyot, or flat-topped seamount. No marine geologist even suspected the existence of these isolated mountains until they were discovered by geologist Harry H. Hess in 1946.
He was serving at the time as naval officer on a ship equipped with a fathometer. Hess named these truncated peaks for the nineteenth-century Swiss-born geologist Arnold Guyot, who had served on the faculty of Princeton University for thirty years. Since then, hundreds of guyots have been discovered in every ocean but the Arctic. Like offshore canyons, guyots present a challenge to oceanographic theory. They are believed to be extinct volcanoes. Their flat tops indicate that they once stood above or just below the surface, where the action of waves leveled off their peaks. Yet today, by definition, their summits are at least 600 feet below the surface, and some are as deep as 8,200 feet. Most lie between 3,200 feet and 6,500 feet. Their tops are not really flat but slope upward to a low pinnacle at the center. Dredging from the tops of guyots has recovered basalt and coral rubble, and that would be expected from the eroded tops of what were once islands. Some of this material is over 80 million years old. Geologists think the drowning of the guyots involved two processes: The great weight of the volcanic mountains depressed the sea floor beneath them, and the level of the sea rose a number of times, especially when the last Ice Age ended, some 8,000 to 11,000 years ago.

According to the passage, most guyots are found at a depth of ..............