问题
选择题
is more important is as the earth cooled down, water began to appear on its surface.
A．What /that
B．That/what
C．What / what
D．That / that
答案
答案：A
本题考查名词性从句。第一个空是一个缺少空语的主语从句，第二空是一个表语从句，表语从句又是一个as引导的时间状语从句。因此答案是A。