第二节（共2小题，每题2分，满分10分。）
根据短文的内容，从短文后的选项中选出能填入空白处的最佳选项。并在答题卡上相应的位置将该项涂黑，选项中有两项为多余项。
April 22 is Earth Day. 71
The earth has warmed by about 10F（华氏度）over the past 100 years, but why and how? Well, scientists are not quite sure. 72 But many scientists say that people are doing many things which make the earth warmer.
