Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions.

Successful students often do the following while studying. First, they have an overview before reading. Next, they look for important information and pay greater attention to it (which often needs jumping forward or backward to process information). They also relate important points to one another. Also, they activate and use their prior knowledge. When they realize that their understanding is not good, they do not wait to change strategies. Last, they can monitor understanding and take action to correct or "fix up" mistakes in comprehension.

Conversely students with low academic achievement often demonstrate ineffective study skills. They tend to assume a passive role in learning and rely on others (eg, teachers, parents) to monitor their studying, for example, low achieving students often do not monitor their understanding of content they may not be aware of the purpose of studying, and they show little evidence of looking back, or employing "fix-up strategies to fix understanding problems.

Students who struggle with learning new information seem to be unaware that they must extent effort beyond simply reading the content to understand and remember it. Children with learning disabilities do not plan and judge the quality of their studying. Their studying may be disorganized. Students with learning problems face challenges with personal organization as well. They often have difficulty keeping track of materials and assignments, following directions, and completing work on time. Unlike good studiers who employ a variety of study skills in a flexible yet purposeful manner, low-achieving students use a restricted range of study skills. They cannot explain why good study strategies are important for learning, and they tend to use the same, often ineffective study approach for all learning tasks, ignoring task content, structure or difficulty.

According to the passage, what can be learnt about passive students?

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks. 
       A little while ago, the European Parliament recommended a list of 8 key competencies which they believe all (23) ____ institutions should provide their students with, to promote lifelong learning. These key competencies consist of knowledge, skills, and attitudes which are central to the development of (24) ____ children, young people and eventually adults.
       Finland isn't the first country to recognize the value of ‘lifelong learning’ but Finland is the first country to base their teaching curriculum (25) ____ the eight key competencies. Instead of focusing on classic academic subjects, like. History or English, Finnish schools will now structure lessons around broader, crosscutting and interdisciplinary "topics".
       Speaking on why Finland decided to make this shift towards lifelong learning. Pasi Sahlberg. Visiting Professor at the Graduate School of Education Harvard University, said: “educators in Finland think, quite correctly, that schools should teach what young people need in their lives... (26) ______Finnish youth need more than before are more integrated knowledge and skills about real world issues”.
       As Professor Sahlberg explains the key competencies don't focus on knowledge acquisition and test score results, (27) ____ on developing skills for longer term learning, with an emphasis on social and emotional development.

Pasi Sahlberg. Visiting Professor at the Graduate School of Education Harvard University, said: “educators in Finland think, quite correctly, that schools should teach what young people need in their lives... (26) ______

Read the following passage and choose among A, B, C or D the correct answer to each of the questions.

In my experience, freshmen today are different from those I knew when I started as a counselor and professor 25 years ago. College has always been demanding both academically and socially. But students now are less mature and often not ready for the responsibility of being in college.

It is really too easy to point the finger at parents who protect their children from life's obstacle. Parents, who handle every difficulty and every other responsibility for their children writing admission essays to picking college courses, certainly may contribute to their children's lack of coping strategies. But we can look even more broadly to the social trends of today.

How many people do you know who are on medication to prevent anxiety or depression? The number of students who arrive at college already medicated for unwanted emotions has increased dramatically in the past 10 years. We, as a society, don't want to "feel" anything unpleasant and we certainly don't want our children to "suffer".

The resulting problem is that by not experiencing negative emotions, one does not learn the necessary skills to tolerate and negotiate adversity. As a psychologist, I am well aware of the fact that some individuals suffer from depression and anxiety and can benefit from treatment, but I question the growing number of medicated adolescents today.

Our world is more stressful in general because of the current economic and political realities, but I don't believe that the college experience itself is more intense today than that of the past 10 years. What I do think is that many students are often not prepared to be young "adults" with all the responsibilities of life.

What does this mean for college faculty and staff? We are required to assist in the basic parenting of these students - the student who complains that the professor didn't remind her of the due date for an assignment that was clearly listed on the syllabus and the student who cheats on an assignment in spite of careful instructions about plagiarism.

As college professors, we have to explain what it means to be an independent college student before we can even begin to teach. As parents and teachers we should expect young people to meet challenges. To encourage them in this direction, we have to step back and let them fail and pick themselves up and move forward. This approach needs to begin at an early age so that college can actually be a passage to independent adulthood.

The word "handle" in parapgraph 2 mostly means ____.

Read the passage below and choose one correct answer for each question.

Scientists believe they now have scientific evidence to prove that ecosystems work better when there is a greater variety of species within them. This biodiversity loss destroys natural mechanisms that could repair the damage caused by man.

Findings show that losing plants and animals is not only reducing our quality of life but actually endangering our very existence. We cut down rich rain-forests and replace them with one species plantations, such as pine and eucalyptus. We plough up meadows rich in different grasses and herbs and replace them with one grass, for instance, rye or wheat.

When a natural ecosystem is simplified the basic processes in the ecosystem are altered arid even damaged. Without their biodiversity, they are not able to serve as the natural cleaners of our planet. No longer are they able to absorb the carbon dioxide that is being produced in excess. The result is global warming, caused by the increase in the "greenhouse effect", and ultimately, or even sooner, there will be a change in the world's climate.

What is the purpose of paragraph 2?

Read the passage and choose the best answer to compete each of the statements that follow
The hippopotamus is the third largest land animal, smaller only than the elephant and the rhinoceros. Its name comes from two Greek words which mean "river horse". The long name of this animal is often shortened to the easier to handle term "hippo."
The hippo has a natural affinity for the water. It does not float on top of the water; instead, it can easily walk along the bottom of a body of water. The hippo commonly remains underwater for three to five minutes and has been known to stay under for up to half an hour before coming up for air.
In spite of its name, the hippo has relatively little in common with the horse and instead has a number of interesting similarities in common with the whale. When a hippo comes up after a stay at the bottom of a lake or river, it releases air through a blowhole, just like a whale. In addition, the hippo resembles the whale in that they both have thick layers of blubber for protection and they are almost completely hairless.

The expression "has relatively little in common" could be best replaced by____

Overpopulation, the situation of having large numbers of people with too few resources and too little space, is closely associated with poverty. It can result from high population density, or from low amounts of resources, or from both. Excessively high population densities put stress on available resources. Only a certain number of people can be supported o a given area of land, and that number depends on how much food and other resources the land can provide. In countries where people live primarily by means of simple farming, gardening, herding, hunting, and gathering, even large areas of land can support only small numbers of people because these labor - intensive subsistence activities produce only small amounts of food.

In developed countries such as the United States, Japan and the countries of Western Europe, overpopulation generally is not considered a major cause of poverty. These countries produce large quantities of food through mechanized farming, which depends on commercial fertilizers, large - scale irrigation, and agricultural machinery. This form of production provides enough food to support the high densities of people in metropolitan areas.

A country's level of poverty can depend greatly on its mix of population density and agricultural productivity. Bangladesh, for example, has one of the world's highest population densities, with 1,147 persons per sq km. A large majority of the people of Bangladesh engage in low - productivity manual farming, which contributes to the country's extremely high level of poverty. Some of the smaller countries in Western Europe, such as the Netherlands and Belgium, have high population densities as well. These countries practice mechanized farming and are involved in high - tech indutries, however, are therefore have high standards of living.

At the other end of the spectrum, many countries in sub - Saharan Africa have population densities of less than 30 persons per sq km. Many people in these countries practice manual subsistence farming, these countries also have infertile land, and lack the economic resources and technology to boost productivity. As a consequence, these nations are very poor. The United States has both relatively low population density and high agricultural productivity; it is one of the world's weathiest nations.

High birth rates contribute to overpopulation in many developing countries. Children are assets to many poor families because they provide labor, usually for farming. Cultural norms in traditionally rural societies commonly sanction the value of large families. Also, the goverments of developing countries often provide little or no support, financial or political, for farming planning; even people who wish to keep their families small have difficulty doing so. For all those reasons, developing countries tend to have high rates of population growth.

Which of tho following is given as a definition of paragraph 1?

Choose the best answer to complete the passage.

Most people (1) ____ learning with formal education at school, college, university etc. We are all told, from an early age, that we should get a good education'. Generally speaking, it is true that a formal education and the resulting qualifications are important. Education may (2) ____ our potential to find better, more satisfying jobs, earn more and perhaps, become more successful in our chosen career.

However, 'schooling' is only one type of learning. There are many other opportunities to further your (3) ____ and develop the skills you need throughout life. Knowledge can be acquired and skill sets developed anywhere - learning is unavoidable and happens all the (4) ____. However, lifelong learning is about creating and maintaining a positive attitude to learning both for personal and professional development.

Lifelong learners are self-motivated to learn and develop because they want to. (5) ____ learning can enhance our understanding of the world around us, provide us with more and better opportunities and improve our quality of life. People learn for personal development and for professional (6) ____. There are many reasons why people learn for personal development. You may want to increase your knowledge or (7) ____ around a particular hobby or pastime that you enjoy. Perhaps you want to develop some entirely new skill that will in some way enhance your life – take a pottery (8) ____ car mechanic course for example. Perhaps you want to research a medical condition or your ancestry.

If you do find yourself unemployed, then use the time wisely. Learning something new can pay off with new opportunities which might not otherwise have (9) ____. While you are employed, take advantage of training, coaching or mentoring opportunities and work on your continuous professional development as you will likely (10) ____ better at what you do and more indispensable to your current or future employer.

(6) ____

Choose the letter A, B, C or D to complete the passage below

   Since China adopted its open-door (1) _____ approximately twenty-five years ago, Chinese higher education has begun once again to draw closer to the (2) _____ Western world. China's (3) _____ to send scholars and students to the United States at the end of the 1970s, after thirty years of hostility between the two countries, marked a dramatic turning (4) _____ in the nation's educational history. Today, about 50,000 Chinese students, are studying in the United States, accounting (5)_____ 10 percent of the total international students in the country.

(4).................

Plants and animals will find it difficult to escape from or adjust to the effect of global warming, Scientists have already observerd shifts in the lifecycles of many plants and animals, such as flowers blooming earlier and birds hatching earlier in the spring. Many species have begun shifting where they live or their annual migration patterns due to warmer temperatures.
With further warming, animals will tend to migrate toward the poles and up mountainsides toward higher elevations. Plants will also attempt to shift their ranges, seeking new areas as old habitats grow too warm. In many places, however, human development will prevent these shifts. Species that find cities or farmland blocking their way north or south may become extinct. Species living in unique ecosystems, such as those found in polar and mountantop regions, are especially at risk because migration to new habitats is not possible. For example, polar bears and marine mammals in the Arctic are already threatened by dwindling sea ice but have nowhere farther to go.
Projecting species extinction due to global warming is extremely difficult. Some scientists have estimated that 20 to 50 percent of species could be committed to extiction with 2 to 3 Celsius degrees of further warming. The rate of warming, not just the magnitude, is extremely important for plants and animals. Some species and even entire ecosystems, such as certain types of forest, many not be able to adjust quickly enough and may disappear.
Ocean ecosystems, especially fragile ones like coral reefs, will also be affected by global warming. Warmer ocean temperatures can cause coral to "bleach", a state which if prolonged will lead to the death of the coral. Scientists estimate that even 1 Celsius degree of additional warming could lead to widespread bleaching and death of coral reefs around the world. Also increasing carbon dioxide in the atmosphere enters the ocean and increases the acidity of ocean waters. This acidification furter stresses ocean ecosystems.

The word “fragile” in paragraph 4 most probably means....................

Chọn từ thích hợp điền vào chỗ trống:

THE THREAT TO THE ENVIRONMENT

Nowadays people are more aware that wildlife all over the world is in danger. Many (1)________of animals are threatened, and could easily become (2)______ if we do not make an effort to protect them. There are many (3)_______ for this. In some cases, animals are hunted for their fur or for othervaluable parts of their bodies. Some birds, such as parrots, are caught (4)________and sold as pets. For many animals and birds, the problem is that their habitat - the (5)________where they live - is disappearing. More (6)________is used for farms, for houses or industry, and there are fewer open (7)________than there once were. Farmers use powerful chemicals to help them grow better (8)________, but these chemicals pollute the environment and (9)________wildlife. The most successful animals on earth - human beings - will soon be the only Ones left, unless we can (10)________this problem.

(8)________

The Sun today is a yellow dwarf star. It is fueled by thermonuclear reactions near its center that convert hydrogen to helium. The Sun has existed in its present state for about four billion six hundred million years and is thousands of times larger than the Earth.
By studying other stars, astronomers can predict what the rest of the Sun's life will be like.
About five billion years from now, the core of the Sun will shrink and become hotter. The surface temperature will fall. The higher temperature of the center will increase the rate of thermonuclear reactions. The outer regions of the Sun will expand approximately 35 million miles, about the distance to Mercury, which is the closest planet to the Sun. The Sun will then be a red giant star. Temperatures on the Earth will become too high for life to exist.
Once the Sun has used up its thermonuclear energy as a red giant, it will begin to shrink. After it shrinks to the size of the Earth, it will become a white dwarf star. The Sun may throw off huge amounts of gases in violent eruptions called nova explosions as it changes from a red giant to a white dwarf.
After billions of years as a white dwarf, the Sun will have used up all its fuel and will have lost its heat. Such a star is called a black dwarf. After the Sun has become a black dwarf, the Earth will be dark and cold. If any atmosphere remains there, it will have frozen over the Earth’s surface.

When the Sun has used up its energy as a red giant, it will ....................

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

"Nowadays people are more aware that wildlife all over the world is in (1)….  . Many species of animals are threatened, and could easily become (2)….   if we do not make an effort to (3)….. them. There are many reasons for this. In some cases, animals are (4)….. for their fur or for other valuable parts of their bodies. Some birds, such as parrots, are caught (5)…. , and sold as pets. For many animals and birds, the problem is that their habitats - the place where they live - is (6)…. . More (7)….  is used for farms, for houses and industry, and there are fewer open spaces than there once were. Farmers use powerful Chemicals to help them grow better (8)…. , but these Chemicals pollute the environment and (9)… wildlife. The most successful animals on Earth, human beings, will soon be the only ones (10)….. unless we can solve this problem."

10. The most successful animals on Earth, human beings, will soon be the only ones (10)….. unless we can solve this problem.

Choose the best answer to complete the passage.

Most people (1) ____ learning with formal education at school, college, university etc. We are all told, from an early age, that we should get a good education'. Generally speaking, it is true that a formal education and the resulting qualifications are important. Education may (2) ____ our potential to find better, more satisfying jobs, earn more and perhaps, become more successful in our chosen career.

However, 'schooling' is only one type of learning. There are many other opportunities to further your (3) ____ and develop the skills you need throughout life. Knowledge can be acquired and skill sets developed anywhere - learning is unavoidable and happens all the (4) ____. However, lifelong learning is about creating and maintaining a positive attitude to learning both for personal and professional development.

Lifelong learners are self-motivated to learn and develop because they want to. (5) ____ learning can enhance our understanding of the world around us, provide us with more and better opportunities and improve our quality of life. People learn for personal development and for professional (6) ____. There are many reasons why people learn for personal development. You may want to increase your knowledge or (7) ____ around a particular hobby or pastime that you enjoy. Perhaps you want to develop some entirely new skill that will in some way enhance your life – take a pottery (8) ____ car mechanic course for example. Perhaps you want to research a medical condition or your ancestry.

If you do find yourself unemployed, then use the time wisely. Learning something new can pay off with new opportunities which might not otherwise have (9) ____. While you are employed, take advantage of training, coaching or mentoring opportunities and work on your continuous professional development as you will likely (10) ____ better at what you do and more indispensable to your current or future employer.

(1) ____

Chọn từ thích hợp điền vào chỗ trống:

THE THREAT TO THE ENVIRONMENT

Nowadays people are more aware that wildlife all over the world is in danger. Many (1)________of animals are threatened, and could easily become (2)______ if we do not make an effort to protect them. There are many (3)_______ for this. In some cases, animals are hunted for their fur or for othervaluable parts of their bodies. Some birds, such as parrots, are caught (4)________and sold as pets. For many animals and birds, the problem is that their habitat - the (5)________where they live - is disappearing. More (6)________is used for farms, for houses or industry, and there are fewer open (7)________than there once were. Farmers use powerful chemicals to help them grow better (8)________, but these chemicals pollute the environment and (9)________wildlife. The most successful animals on earth - human beings - will soon be the only Ones left, unless we can (10)________this problem.

(6)________

Overpopulation, the situation of having large numbers of people with too few resources and too little space, is closely associated with poverty. It can result from high population density, or from low amounts of resources, or from both. Excessively high population densities put stress on available resources. Only a certain number of people can be supported o a given area of land, and that number depends on how much food and other resources the land can provide. In countries where people live primarily by means of simple farming, gardening, herding, hunting, and gathering, even large areas of land can support only small numbers of people because these labor - intensive subsistence activities produce only small amounts of food.
In developed countries such as the United States, Japan and the countries of Western Europe, overpopulation generally is not considered a major cause of poverty. These countries produce large quantities of food through mechanized farming, which depends on commercial fertilizers, large - scale irrigation, and agricultural machinery. This form of production provides enough food to support the high densities of people in metropolitan areas.
A country's level of poverty can depend greatly on its mix of population density and agricultural productivity. Bangladesh, for example, has one of the world's highest population densities, with 1,147 persons per sq km. A large majority of the people of Bangladesh engage in low - productivity manual farming, which contributes to the country's extremely high level of poverty. Some of the smaller countries in Western Europe, such as the Netherlands and Belgium, have high population densities as well. These countries practice mechanized farming and are involved in high - tech indutries, however, are therefore have high standards of living.
At the other end of the spectrum, many countries in sub - Saharan Africa have population densities of less than 30 persons per sq km. Many people in these countries practice manual subsistence farming, these countries also have infertile land, and lack the economic resources and technology to boost productivity. As a consequence, these nations are very poor. The United States has both relatively low population density and high agricultural productivity; it is one of the world's weathiest nations.
High birth rates contribute to overpopulation in many developing countries. Children are assets to many poor families because they provide labor, usually for farming. Cultural norms in traditionally rural societies commonly sanction the value of large families. Also, the goverments of developing countries often provide little or no support, financial or political, for farming planning; even people who wish to keep their families small have difficulty doing so. For all those reasons, developing countries tend to have high rates of population growth.

The phrase "that number" in paragraph 1 refers to the number of ..................

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:
    Animation traditionally is done by hand-drawing or painting successive frame of an object, each slightly different than the proceeding frame. In computer animation, although the computer may be the one to draw the different frames, in most cases the artist will draw the beginning and ending frames and the computer will produce the drawings between the first and the last drawing. This is generally referred to as computer-assisted animation, because the computer is more of a helper than an originator. 
    In full computer animation, complex mathematical formulas are used to produce the final sequences of pictures. These formulas operate on extensive databases of numbers that defines the objects in the pictures as they exist in mathematical space. The database consists of endpoints, and color and intensity information. Highly trained professionals are needed to produce such effects because animation that obtains high degrees of realism involves computer techniques from three-dimensional transformation, shading, and curvatures.
    High-tech computer animation for film involves very expensive computer systems along with special color terminals or frame buffers. The frame buffer is nothing more than a giant image memory for viewing a single frame. It temporarily holds the image for display on the screen.
    A camera can be used to film directly from the computer’s display screen, but for the highest quality images possible, expensive film recorders are used. The computer computers the positions and colors for the figures in the picture, and sends this information to the recorder, which captures it on film. Sometimes, however, the images are stored on a large magnetic disk before being sent to the recorder. Once this process is completed, it is replaced for the next frame. When the entire sequence has been recorded on the film, the film must be developed before the animation can be viewed. If the entire sequence does not seem right, the motions must be corrected, recomputed, redisplayed, and rerecorded. This approach can be very expensive and time – consuming. Often, computer-animation companies first do motion tests with simple computer-generated line drawings before selling their computers to the task of calculating the high-resolution, realistic-looking images.

The word “Once” in the fourth paragraph is closest in meaning to ______.

Read the passage below and decide whether the statements are TRUE or FALSE?

   According to the Academic Ranking of World Universities, more than 30 of the highest-ranked 45 institutions are in the United States, as measured by awards and research output. Public universities, private universities, liberal arts colleges, and community colleges all have a significant role in higher education in the United States. An even stronger pattern is shown by the Webometrics Ranking of World Universities with 103 US universities in the World's Top 200 universities.

   The 2006 American Community Survey conducted by the United States Census Bureau found that 19.5 percent of the population had attended college but had no degree, 7.4 percent held an associate's degree, 17.1 percent held a bachelor's degree, and 9.9 percent held a graduate or professional degree.

   Educational attainment in the United States is similar to that of other developed countries. Colleges and universities in the U.S. vary in terms of goals: some may emphasize a vocational, business, engineering, or technical curriculum while others may emphasize a liberal arts curriculum. Many combine some or all of the above. Students can apply to some colleges using the Common Application. There is no limit to the number of colleges or universities to which a student may apply, though an application must be submitted for each.'

20 percent of the population had attended college but had no degree

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions. 
       In “How many hours does it take to make a friend?” (2018), Jeffrey A. Hall describes the types of encounters that build a friendship.
       His study found that hours of time spent together was linked with closer friendships, as was time spent enjoying leisure activities together. Specifically, he found that the chance of making a “casual friend,” as opposed to a mere acquaintance, was greater than 50 percent when people spent approximately 43 hours together within three weeks of meeting. He further found that casual friends evolve into friends at some point between 57 hours after three weeks, and 164 hours over three months. Hall's research also demonstrated, however, that when it comes to time spent developing friendships, quality is more important than quantity. And when it comes to conversation, topics matter. When it comes to building quality relationships, the duration of conversation is not as important as the content. Meaningful conversation is the key to bonding with others. 
       Hall found that when it comes to developing friendships, sharing daily life through catching up and joking around promotes closeness; small talk does not. Consider the inane topics that often come up when you are trapped in an elevator with an acquaintance. Discussing the weather or speculating on how many stops you will make before finally reaching the lobby does not facilitate bonding. Nor does mere proximity. Hall found that obligatory time spent together, such as in a classroom or workplace, does not promote closeness. Friendships require an efficient use of time together. Someone who remembers the details of your life and asks questions about your family, your job, your latest vacation, etc., is much more likely on his or her way to becoming someone you consider a friend, as opposed to an acquaintance.

According to paragraph 2, what conclusion can be drawn from the finding of Jeffrey A. Hall?

Choose the best answer

The World Wide Fund for Nature (WWF) is an international (1) ____ governmental organization for the (2) ____, research, and restoration of the environment. The organization was (3) ____ as a charitable trust on September 11, 1961, in Morges, Switzerland, under the name World Wildlife Fund. It was an initiative of Julian Huxley and Max Nicholson. It is the world's largest independent conservation organization with over 5 million (4) ____ worldwide, working in more (5) ____ 90 countries, supporting 100 conservation and environmental projects around the world. It is a charity, with (6) ____ 9% of its funding coming from voluntary, (7) ____ by private individuals and businesses.

The group says its mission is "to halt and reverse the (8) ____ of our environment". Currently, much of its work focuses on the conservation of three biomes that contain most of the world's biodiversity: forests, freshwater ecosystems, and oceans and coasts. Among other issues, it is also concerned (9) ____ endangered species, pollution, and climate change. The organization (10) ____ more than 20 field projects worldwide. In the last few years, the organization set up offices and operations around the world.

(1) ____

Choose the best answer to complete the passage.

LEARNING HOW TO LEARN AND THINK

What is the point of the education system? Although this question may seem ridiculous at first (1) ____, it is actually not stupid as it sounds. The reason it is (2) ____ trying to answer is that schools and university clearly (3) ____ academic achievement, passing exams and gaining (4) ____ much more than acquiring skills such as (5) ____ children or car maintenance. But why is it? Why do they neglect to teach (6) ____ skills at school?

One answer may be that schools don't (7) ____ to help us gain useful knowledge about the world. At school, what we are (8) ____ learning is how to learn effectively. The idea is that we can then (9) ____ use of that ability later on in life when we come to deal (10) ____ more practical aspects of day- to-day living.

However, some people argue that the (11) ____ system is in fact a failure because it doesn't actually teach children how to become good thinkers. Learning how to learn is one thing. Learning how to learn is one thing. Learning how to think is (12) ____ another.

(12) ____

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions: 
We are descendents of the ice age. Periods of glaciation have spanned the whole of human existence for the past 2 million years. The rapid melting of the continental glaciers at the end of the last ice age spurred one of the most dramatic climate changes in the history of the planet. During this interglacial time, people were caught up in a cataclysm of human accomplishment, including the development of agriculture and animal husbandry. Over the past few thousand years, the Earth’s climate has been extraordinarily beneficial, and humans have prospered exceedingly well under a benign atmosphere. Ice ages have dramatically affected life on Earth almost from the very beginning. It is even possible that life itself significantly changed the climate. All living organisms pull carbon dioxide out of the atmosphere and eventually store it in sedimentary rocks within the Earth’s crust. If too much carbon dioxide is lost, too much heat escapes out into the atmosphere. This can cause the Earth to cool enough for glacial ice to spread across the land. In general the reduction of the level of carbon dioxide in the atmosphere has been equalized by the input of carbon dioxide from such events as volcanic eruptions. Man, however, is upsetting the equation by burning fossil fuels and destroying tropical rain forests, both of which release stored carbon dioxide. This energizes the greenhouse effect and causes the Earth to warm. If the warming is significant enough, the polar ice caps eventually melt. The polar ice caps drive the atmospheric and oceanic circulation systems. Should the ice caps melt, warm tropical waters could circle the globe and make this a very warm, inhospitable planet. Over the past century, the global sea level has apparently risen upwards of 6 inches, mainly because of the melting of glacial ice. If present warming trends continue, the seas could rise as much as 6 feet by the next century. This could flood coastal cities and fertile river deltas, where half the human population lives. Delicate wetlands, where many marine species breed, also would be reclaimed by the sea. In addition, more frequent and severe storms would batter coastal areas, adding to the disaster of the higher seas. The continued melting of the great ice sheets in polar regions could cause massive amounts of ice to crash into the ocean. This would further raise the sea level and release more ice, which could more than double the area of sea ice and increase correspondingly the amount of sunlight reflected back into space. The cycle would then be complete as this could cause global temperatures to drop enough to initiate another ice age.

The word “this” in the third paragraph refers to.....................