问题补充：
April 22 is Earth Day. Everyone on Earth should care about and protect the earth!
The earth has warmed by about 1°F (华氏度) over the past 100 years, but why and how?
Well, scientists are not quite sure. Maybe the earth gets warmer and warmer on its own. But many scientists say that people are doing many things which makes the earth warmer.
First, greenhouse effect (温室效应) is a very important reason for the change of the earth. People give out too much energy into the air every year. It makes the earth warmer. Climate (气候) change is another important reason. Sometimes it becomes too hot and sometimes too cold. Sometimes there is too much rain and sometimes too little. The change of the climate makes the earth warmer. In turn, the warmth of the earth changes the climate, too.
When the earth becomes warmer, there may be more rain and a rise in sea level. It will affect the growth of plants, animals and people. On a Pacific island, 100 people have to move to higher ground because the sea is rising. These people can no longer live on the coast. Before that, two islands without people went underwater in 1999. Scientists say that the seas can rise by nearly one metre by 2100.
People can affect the earths air, land and water. As for us, we can do many things to protect the earth. For example, we can use fridges less. We can tell more people about protecting the earth.
【小题1】Earth Day is probably set for people to .A．learn more about the earthB．make full use of the earthC．take better care of the earth.D．study the warmth of the earth【小题2】We can infer (推断) from the passage that the reasons for the warmer earth are
now.A．not very clear B．completely secretC．well knownD．not given yet【小题3】Greenhouse effect comes from.A．sea risingB．climate changeC．natures unbalanceD．peoples activity【小题4】The passage mainly tells us that .A．there is more rain nowB．we should protect the earthC．we must stop pollutionD．sea level is getting higherC
答案：
(答案→)C
解析：这篇短文中作者主要分析了地球变暖的原因，并号召我们行动起来保护地球。
【小题1】根据April 22 is Earth Day. Everyone on Earth should care about and protect the earth!描述，可知选C。
【小题2】根据Well, scientists are not quite sure. Maybe the earth gets warmer and warmer on its own. 描述，可知地球变暖的原因还不太清楚，故选A。
【小题3】根据People give out too much energy into the air every year. It makes the earth warmer.描述，可知温室效应来自于人类的活动，故选D。
【小题4】这篇短文中主要分析了地球变暖的原因，告诉我们应该保护地球。故选B。
