【题目】__________ is even more important is _________ the earth cooled down, water began to appear on its surface.
A. What; that as B. It; which
C. It; which as D. What; which
在线课程【答案】A
【解析】
试题分析：考查名词性从句。句意是：更重要的是由于地球变冷，水开始出现在它的表面。第一空是主语从句，缺少引导词，缺少主语，所以填what；第二空是表语从句，从句不缺成分，只缺引导词，所以填that；在表语从句中包含一个as引导的原因状语从句。故选A。