南京师范大学04年4月英语二资料7

　　「习题一」

　　1

　　What is color？ Why do some objects look red， others green，  others blue？

　　Color is caused by reflected light rays. We see color because objects reflect light. Something that is red reflects mostly red light. （It reflects a little green of blue light， too， but we do not see it.） In the same way， a green object reflects mostly green light. White objects reflect all colors of light Black objects do not reflect any light.

　　What happens to the colors of light that are not reflected？ They are absorbed by the object. The darker the color， the less light is reflected and the more light is absorbed. Light that is absorbed is turned into heat. For this reason， dark-colored clothes are warmer in the sunlight than light-colored clothes.

　　2

　　The sum spent on books and magazines seems small. Most families take at least one daily newspaper and a Sunday paper. They may take several weekly magazines， usually including the Radio Times （《无线电节目报》）。 This gives them the weekly programmers of the B.B.C. The small sum spent on books does not mean that people do very little reading. Millions of cheap， paper-backed（平装的） books are bought every month. There are good public libraries everywhere from which books may be borrowed. Over one million books are taken out from these libraries every week-day. In some homes， however， there is less serious reading now than there was fifty years ago. Many people prefer to listen to the radio， or look at films or television. Many people seem to prefer popular picture magazines to magazines that contain serious reading.

　　3

　　Astronomers（天文学家） can tell just how hot the surface of the moon gets. The side of the moon toward the sun gets two hundred degrees hotter than boiling water. The night side reaches 243 degrees below zero.

　　In the eclipse（月食）， the earth‘s shadow fails on the moon. Then the moon’s temperature may drop 300 degrees in a very short time.

　　A temperature change like this cannot happen on the earth. Why does it happen on the moon？  Astronomers think that the surface of the moon is dust. On the earth， rocks store heat from the sun. When the sun goes down， the rocks stay warm. But the dust of the moon cannot store heat. So when the moon gets dark， the heat escapes quickly. The moon gets very cold.

　　4

　　Water is very important to living things. Without water there can be no life on Earth. All animals and plants need water. Man also needs water. We need water to drink， to cook our food and to clean ourselves. Water is needed in offices， factories and schools. Where else is water needed？

　　Water covers about seventy percent of the Earth‘s surface. There is water is seas， rivers， lakes， springs（泉） and wells.

　　Water is found almost everywhere.  Even in the driest part of the world there is some water in the air. You cannot see it or feel it when it is part of the air. The water in oceans and lakes and streams is a liquid. The water in the air is not a liquid but a gas. We call it water vapor.

　　Clouds are made of water. They may be made of tiny drops of water. They may also be made of snow crystals. Snow crystals are tiny crystals of ice. Ice is frozen water or water that has become solid.

　　「习题一答案」

　　1   颜色是什么？为什么有些东西看起来是红色，另一些是绿色，还有些是蓝色的呢？

　　颜色是由反射出的光线引起的。我们能看出颜色，是因为物体能反射光。红色物体主要反射红光。（它也反射一点绿光或蓝光，但我们看不见。）同样，绿色物体主要反射绿光。白色物体反射所有颜色的光。黑色物体不反射任何光。

　　那些没有被反射的光的颜色怎么样了呢？他们被物体吸收了。颜色越深，反射的光就越少，吸收的光也就越多。被吸收的光变成热。正因如此，在阳光下，深色衣服比浅色衣服更保暖。

　　2   用于购买书籍杂志的钱看来很少，大多数家庭至少订一份日报和一份周日版的报纸。他们也可能订几份周刊，通常包括《无线电节目报》。这就可以使他们知道 BBC每周的节目。在书籍上开销少，并不是说人们不怎么看书。每月都出数以百万计的平装廉价书。各处都有良好的公共图书馆，可以从中借书。这些图书馆每个工作日都借出一百多万册书籍。然而比起五十年前，有些家庭读书不那么认真了。许多人情愿听广播或者看电影或电视。许多人似乎情愿看通俗画报，而不看刊载严肃读物的杂志。

　　3   天文学家能说出月球表面有多热。月球面对太阳的那一面要比沸水热200度。黑夜的那一面达到零下243度。

　　月食时，地球阴影落在月球上。月球温度可以在短时间内下降300度。

　　像这样的温度变化不可能发生在地球上。它为什么会出现在月球上呢？天文学家认为，月球表面上是尘埃。在地球上，岩石贮存来自太阳的热量。太阳落山后，岩石仍保持一定温度。但是月球的尘埃不能贮存热量。因此当月球变黑以后，热量很快消散。月球就变得非常寒冷。

　　4   水对生物来说是至关重要的。没有水，地球上就不可能有生命。一切动植物都需要水。人也需要水。我们要喝水，用水烧饭和洗澡。机关、工厂和学校也需要水。还有别的什么地方需要水呢？

　　水约占地球表面总面积的百分之七十。海洋、河流、湖泊、泉眼和井里都有水。

　　水几乎到处可见。即使在世界上最干旱的地方，空气中也有水。当水存在于空气中时是看不见摸不着的。海洋、湖泊和溪流中的水呈液态。空气中的水不是液态，而是气态，我们管它叫水蒸汽。

　　云是由水形成的。它们可能是由小水滴形成的，也可能是由雪晶形成的。雪晶是细小的冰晶。冰是冻结的水或是已变成固态的水。

　　「习题二」

　　1 Finding enough meat was a problem for primitive man （原始人） . Keeping it for times when it was scarce （短缺的）was just as hard. Three ways were found to keep meat from spoiling： salting， drying and freezing.

　　People near salty waters salted their meat. At first they probably rubbed dry salt on it， but this preserved only the outside. Later they may have pickled （腌制） their meat by soaking it in salt water.

　　In hot， dry lands， men found that they could eat meat that had dried while it was still on the bones. They later learned to cut meat into strips and hang it up to dry in the hot air.

　　Men in cold climates found that frozen meat did not spoil. They could leave their meat outside and eat it when they pleased.

　　2 Strange things happen to time when you travel， because the earth is divided into twenty-four time zones （时区）， one hour apart. You can have days with more or fewer than twenty-four hours， and weeks with more or fewer than seven days.

　　If you make a five-day drip across the Atlantic Ocean（大西洋）， your ship enters a different time zone every day. As you enter each zone， the time changes one hour. Traveling west， you set your clock back； traveling east， you set it ahead. Each day of your trip has either twenty-five or twenty-three hours.

　　If you travel by ship across the Pacific（太平洋），  you cross the international date line（国际日期变更线）。 By agreement， this is the point where a new day begins. When you cross the line， you change your calendar one full day， backward or forward. Traveling east， today becomes yesterday； traveling west， it is tomorrow！

　　3 Volcanoes have been erupting（喷发） on the earth for millions of years. More than five hundreds still erupt today. These are called active volcanoes. Volcanoes are located in belts or chains. They are found where the earth‘s crust is weak. The weak spots let the hot rock escape when the volcano erupts.

　　Many volcano belts are mountain ranges along the edges of continents. One pest runs along the western coast of South American up through tire western part of the United States. Other volcanoes are found in ocean basins（盆地）。

　　About three-fifths of all active volcanoes in the world are in the Pacific Ocean（太平洋）。 Many of these volcanoes erupt under the water. The Hawaiian Island（夏威夷群岛） were built by volcanoes that began erupting under water and