题目

白菜等植物在沙漠中难以生存，使它们不在沙漠分布的主要因素是。（ ） A . 土壤 B . 温度 C . 水分 D . 阳光 答案：CThey often have problems with______.A．what will they be able to doB．what they will be able to do C．that will they have to doD．that will they have to do