预约成功
A greenhouse is a building made of glass which is used for keeping plants warm when the outside temperature is low.In a similar way，there are several gases in the atmosphere which trap the heat generated by the sun and prevent it from escaping.These gases are known as"greenhouse gases"，and the way in which they trap heat in the atmosphere is called the"greenhouse effect".This is not simply air pollution like photochemical smog(光化学烟雾)，for example.Most of the main greenhouse gases occur naturally in small amounts in our atmosphere，and without them the earth would be thirty degrees colder and human life would not exist.In other words，the greenhouse effect is a natural process which is to some extent beneficial to us.
The problem is that in the last century and a half，we have been putting excessive amounts of these gases into the earth's atmosphere by burning large quantities of coal and oil and by cutting down forests.In 1850，there were 280 parts per million of carbon dioxide(二氧化碳)in the atmosphere.Now there are 360，and this figure is expected to rise to 460 by the year 2030.We now put 24 billion metric(公制的)tons of carbon dioxide into the atmosphere every year.We have also created a group of artificial greenhouse gases that are 20，000 times more effective than carbon dioxide in trapping heat in the atmosphere.These are the chlorofluorocarbon(氟氯碳)gases，which are used in refrigerators and air conditioning systems.
The rapid increase in greenhouse gases is making the world warmer.The world's temperature has already gone up by half a degree this century，and the sea level has risen by ten centimeters.If the amount of carbon dioxide in the atmosphere doubles，there will probably be a rise in the earth's temperature of between 1~and 4~.This may seem a small increase，but it would be enough to cause major changes in geography and agriculture.Large areas of the world would be flooded，and some regions would become dry and unable to produce crops.It is important，too，to consider that there maybe a delay of about thirty years in the greenhouse effect.This means that we are probably experiencing only now the effect of the gases put into the atmosphere up to the 1960s.Since then，our use of these gases has greatly increased.
1、A small increase in the earth's temperature may bring about
A a decline in agriculture.
B a drop of the sea level.
C the death of all animals.
D a delay in the greenhouse effect.
参考答案：A
2、According to the passage，a greenhouse is built to
A keep the plants warm.
B prevent air pollution.
C stop the greenhouse effect.
D produce useful gases.
参考答案：A
3、According to the passage，chlorofluorocarbon gases differ from carbon dioxide in that
A they are more useful.
B they are much heavier.
C they are more efficient in making the'world colder.
D they are more effective in catching the heat from the sun.
参考答案：D
4、A major cause of the increase in the greenhouse gases is
A the burning of trees and crops.
B the building of many greenhouses.
C the burning of large quantities Of coal and oil.
D the flooding of large areas of the world.
参考答案：C
5、Without the greenhouse gases，the earth would
A become warmer.
B be much colder.
C move more slowly.
D move quickly.
参考答案：B
参考译文：
温室是由玻璃制成的建筑物，当室外温度较低时，用来保持植物的温暖。以同样的方式，大气中也有几种气体，它们将太阳产生的热量收集起来，防止其外泄。这些气体被称为“温室气体”，它们在大气中吸收热量的方式被称为“温室效应”。例如，这不仅仅是像光化学烟雾那样的空气污染。大多数主要的温室气体在我们的大气中自然地以少量的形式存在，没有它们，地球将更冷30度，人类将不存在。换言之，温室效应是一个自然过程，在一定程度上对我们有利。
问题是，在过去的一个半世纪里，我们通过燃烧大量的煤和石油和砍伐森林，向地球大气中排放了过量的这些气体。1850年，大气中二氧化碳(二氧化碳)含量为280份/百万。现在有360个，预计到2030年这个数字将上升到460个。我们现在每年向大气中排放240亿吨二氧化碳。我们还创造了一组人工温室气体，其在吸收大气热量方面的效率是二氧化碳的2万倍。这些是氯氟碳(氟碳)气体，用于冰箱和空调系统。
温室气体的迅速增加使世界变暖。本世纪，世界气温已经上升了半度，海平面上升了十厘米。如果大气中二氧化碳的含量加倍，地球的温度可能会上升到1到4度之间。这似乎是一个小的增长，但足以引起地理和农业的重大变化。世界上的大面积地区将被洪水淹没，一些地区将变得干燥，无法生产作物。同样重要的是，要考虑到温室效应可能会延迟30年左右。这意味着我们现在可能只经历了20世纪60年代之前进入大气层的气体的影响。从那时起，我们对这些气体的使用大大增加了。
