【正文】 大學(xué)英語四級考試Model Test ThreePart Ⅰ WritingDirections: For this part, you are allowed 30 minutes to write a letter. You should write at least 120 words following the outline given below in Chinese: 給你的外國朋友寫一封信，告訴他(她)你已經(jīng)被美國的一所大學(xué)錄取，但你苦惱的是自己的聽力和口語水平不夠，你想尋求他(她)對于如何提高聽和和口語的建議。Part Ⅱ Reading Comprehension (Skimming and Scanning)Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions on Answer Sheet 1. For questions 17, choose the best answer from the four choices marked [A], [B], [C] and [D]. For questions 810, plete tile sentences with the information given in the passage. The EarthPower and Light Compared to the rest of the universe, the Earth is very small. Our planet and eight (or maybe nine) others orbit the Sun, which is only one of about 200 billion stars in our galaxy. Our galaxy, the Milky Way, is part of the universe, which includes millions of other galaxies and their stars and planets. By parison, the Earth is microscopic. Compared to a person, on the other hand, the Earth is enormous. It has a diameter of 7,926 miles (12,756 kilometers) at the equator, and it has a mass of about 61024 kilograms. The Earth orbits the Sun at a speed of about 66,638 miles per hour ( kilometers per second). Don39。t dwell on those numbers too long, though。 to a lot of people, the Earth is inconceivably, mindbogglingly big. And it39。s just a fraction of the size of the Sun. From our perspective on Earth, the Sun looks very small. This is because it39。s about 93 million miles away from us. The Sun39。s diameter at its equator is about 100 times bigger than Earth39。s, and about a million Earths could fit inside the Sun. The Sun is inconceivably, mindbogglingly bigger. But without the Sun, the Earth could not exist, in a sense, the Earth is a giant machine, full of moving parts and plex systems. All those systems need power, and that power es from the Sun. The Sun is an enormous nuclear power sourcethrough plex reactions, it transforms hydrogen into helium, releasing light and heat. Because of these reactions, every square meter of our planet39。s surface gets about 342 Watts of energy from the Sun every year. This is about 1017 Watts total, or as much as billion large power plants could generate. You can learn about how the Sun creates energy in How the Sun Works. When this energy reaches the Earth, it provides power for a variety of reactions, cycles and systems. It drives the circulation of the atmosphere and the oceans. It makes food for plants, which many people and animals eat. Life on Earth could not exist without the Sun, and the planet itself would not have developed without it. To a casual observer, the Sun39。s most visible contributions to life are light, heat and weather.Night and Day Some of the Sun39。s biggest impacts on our planet are also its most obvious. As the Earth spins on its axis, parts of the planet are in the Sun while others are in the shade. In other words, the Sun appears to rise and set. The parts of the world that are in daylight get warmer while the parts that are dark gradually lose the heat they absorbed during the day. You can get a sense of how much the Sun affects the Earth39。s temperature by standing outside on a partly cloudy day. When the Sun is behind a cloud, you fuel noticeably cooler than when it isn39。t. The surface of our planet absorbs this heat from the Sun and emits it the same way that pavement continues to give off heat in the summer after the Sun goes down. Our atmosphere does the same thingsit absorbs the heat that the ground emits and sends some of it back to the Earth. The Earth39。s relationship with the Sun also creates seasons. The Earth39。s axis tips a littleabout degrees. One hemisphere points toward the Sun as the other points away. The hemisphere that points toward the Sun is warmer and gets more lightit39。s summer there, and in the other hemisphere it39。s winter. This effect is less dramatic near the equator than at the poles, since the equator receives about the same amount of sunlight all year. The poles, on the other hand, receive no sunlight at all during their winter months, which is part of the reason why they39。re frozen. Most people are so used to the differences between night and day (or summer and winter) that they take them for granted. But these changes in light and temperature have an enormous impact on other systems on our planet. One is the circulation of air through our atmosphere. For example: The Sun shines brightly over the equator. The air gets very warm because the equator faces the Sun directly and because the ozone layer is thinner there. As the air warms, it begins to rise, creating a low pressure system. The higher it rises, the more the air cools. Water condenses as the air cools, creating clouds and rainfall. The air dries out as the rain falls. The result is warm, dry air, relatively high in our atmosphere. Because of the lower air pressure, air rushes toward the equator from the north and south. As it warms, it rises, pushing the dry air away to the north and the south. The dry air sinks as it cools, creating highpressure areas and deserts to the north and south of the equator. This is just one piece of how the Sun circulates air around the worldocean currents, weather patterns and other factors also play a part. But in general, air moves from highpressure to lowpressure areas, much the way that highpressure air rushes from the mouth of an inflated balloon when you let go. Heat also generally moves from the warmer equator to the cooler poles. Imagine a warm drink sitting on your deskthe air around the drink gets warmer as the drink gets colder. This happens on Earth on an enormous scale. The Coriolis Effect, a product of the Earth39。s rotation, affects this system as well. It causes large weather systems, lik