[外语类试卷]大学英语四级模拟试卷516及答案与解析.doc
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1、大学英语四级模拟试卷 516及答案与解析 一、 Part I Writing (30 minutes) 1 For this part, you are allowed thirty minutes to write a letter. Imagine you are Wang Ting. Write a letter to Xiao Lin, a classmate of yours who is at home and suffering from eye strain (视疲劳 ). However, shes still willing to participate in the fo
2、rth coming CET-4 test. You should write no more than 120 words following the suggestions given below in Chinese. 1. 表示慰问 2. 告知有关你备考的情况 3. 提出你的建议 A Welcome Speech to New Students 二、 Part II Reading Comprehension (Skimming and Scanning) (15 minutes) Directions: In this part, you will have 15 minutes t
3、o go over the passage quickly and answer the questions attached to the passage. For questions 1-7, mark: Y (for YES) if the statement agrees with the information given in the passage; N (for NO) if the statement contradicts the information given in the passage; NG (for NOT GIVEN) if the information
4、is not given in the passage. 1 The Greenhouse Effect Earths climate has been changing constantly over its 5-billion-year history. Sometimes, the climate has warmed so that the oceans have risen and covered much of the Earth. Each of the changes may seem extreme, but they usually occurred slowly over
5、 many thousands of years. Ancient Climate History The first people arrived in America between 151 000 and 30, 000 years ago. During that time, much of North America was covered by great ice sheets. Some 14, 000 years ago, the last ice sheet began to melt very quickly. By 7, 000 years ago, the ice wa
6、s gone. This end to the ice ages caused big changes on the Earth. The changes caused many kinds of plants and animals to die. For example, mastodon-elephant-like animal-and other large mammals that preferred cold climates may not have been able to live in the warmer, drier conditions. The Little Ice
7、 Age Starting in the 14th century, Europeans lived through what is known as the “Little Ice Age.“ The Little Ice Age lasted for several hundred years. During the Little Ice Age, the advance of glaciers along with hard winters and famines caused some people to starve and others to leave their homes.
8、Recent Climate History The Earth has warmed about 1F in the last 100 years. And the four warmest years of the 20th century all happened in the 1990s. Periods of increased heat from the sun may have helped make the Earth warmer. But many of the worlds leading climatologists think that the greenhouse
9、gases people produce are making the Earth warmer, too. Scientists think the sea has risen partly because of melting glaciers and sea ice. When some glaciers melt, they release water into the sea and make it higher than it was before. Scientists also think that warmer temperatures in the sea make it
10、rise even more. Heat makes water expand. When the ocean expands, it takes up more space. What Might Happen? Scientists are not fortune-tellers. They dont know exactly what will happen in the future. But they can use special computer programs to find out how the climate may change in the years ahead.
11、 And the computer programs tell us that the Earth may continue to get warmer. Together, the melting glaciers, rising seas, and computer models provide some good clues. They tell us that the Earths temperature will probably continue to rise as long as we continue increasing the amount of greenhouse g
12、ases in the atmosphere. Scientists have to think like detectives. They look for clues to help them understand how the world works. Then they investigate the clues to find evidence - real facts that can give them a better idea of what is going on. Here are some of the ways that scientists gather evid
13、ence about climate, both past and present: Weather Stations Weather stations help us find out the temperature on the surface of the Earth. Weather stations use special thermometers that tell us the temperature. They can be set up almost anywhere on land. Weather stations also can tell us how fast th
14、e wind is moving and how much rain falls on the ground during a storm. Weather Balloons Almost everyone likes balloons - including scientists! Weather balloons are released to float high up into the atmosphere. They carry special instruments that send all kinds of information about the weather back
15、to people on the ground. Ocean Buoys A buoy is an object that floats on water, and is often used to warn boats away from dangerous places in the ocean or on a river. But some buoys have special instruments on them. These buoys can tell us the temperature and other things about the conditions of the
16、atmosphere. Weather Satellites Humans send satellites into space to travel around the Earth. The satellites send back information to scientists on the ground. Some of the information they give us is about the weather and the Earths temperature. Ice Cores Some scientists who want to find out more abo
17、ut climate study ice for clues. Not just any ice - they are studying the ice from glaciers that have been around for a very long time. They cut pieces of ice and look for air bubbles that were trapped in the ice hundreds or even thousands of years ago. The air bubbles help them discover what the cli
18、mate used to be like on Earth. The evidence they uncover is creating a historical record of regional temperatures and greenhouse gas concentrations dating back 160, 000 years. Sediment Analyses Sediment is the earth and rock that has built up in layers over time. Scientists are learning a great deal
19、 about past climate from studying these layers. Sediment layering pro vides information about where glaciers have been in the past. Ocean sediments provide a map of how ocean currents have flowed in the past. And fossilized pollen found in sediment layers tells us about where different plants have g
20、rown in the past. Tree Rings You can tell how old a tree is by counting its rings because it grows a new ring every year. Tree rings also can tell us how much precipitation fell each year in the place where the tree lives. What Does All of This Mean? Weather stations, balloons, ocean buoys, and sate
21、llites tell us the Earths temperature today. Ice cores, sediment layers, and tree rings tell us about what the Earths climate has been like in the past. With this evidence, scientists are learning how climate changes over time. What Are Scientists Still Unsure About? How do clouds respond to changes
22、 in temperature and precipitation? How do oceans transport heat? How do climate and intense weather events like hurricanes affect each other? As scientists try to answer these and other questions, they will discover many more clues about how the Earths climate system works. It may seem hard to belie
23、ve that people can actually change the Earths climate. But scientists think that the things people do that send greenhouse gases into the air are making our planet warmer. Once, all climate changes occurred naturally. However, during the Industrial Revolution, we began altering our climate and envir
24、onment through agricultural and industrial practices. The Industrial Revolution was a time when people began using machines to make life easier. It started more than 200 years ago and changed the way humans live. Before the Industrial Revolution, human activity released very few gases into the atmos
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