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
网友回答
A. That, that
(答案→)B. What, that
C. What, what
D. 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。