题目

I always figured that comedians were the best kind of people to hang around with as a kid. They tell funny stories, make joke after joke, and happiness seems never to leave them. But time goes on, and we come to see these same people as clowns on the outside, but crying a river in the inside. Comedy from these people comes from a deep pain and sadness in their lives, or out of a deep-seated anger they have at the world around them. Look at Richard Pryor, need I say more? Richard seemed to have everything. For Superman , he ended up getting more money than Christopher Reeve did. Yet he 大面积植树造林不仅美化环境，还能促进生物圈中的水循环，这是因为植物的蒸腾作用可以（　　）A．降低空气的温度B．吸收空气中的二氧化碳C．增加空气中氧的含量D．提高大气湿度，增加降水量