is even important is as the earth cooled down, water began to appear on its surface.A. T

is even important is as the earth cooled down, water began to appear on its surface.
A. That, that
B. What, that
C. What, what
D. It, that

A. That, that(答案→)B. What, thatC. What, whatD. It, that解析：考查名词性从句：句意：甚至更重要的是，随着地球冷却下来，水开始出现在它的表面。第一空是what引导的主语从句，what在主语从句中做主语，第二空是that，连接表语从句，因为表语从句是完整的，不缺成分，选B。

这个问题我还想问问老师呢