托福语法题seasonalrainfall,especiallyinregionsnearthetropics,iswindsthatblowinanoppositedirectioninwinterthaninsummer.A.CausingB.ThatcauseC.TocauseD.Whatcauses我选的A但答案是D,请讲解下这里为什么不

Question

托福语法题
___ seasonal rainfall, especially in regions near the tropics, is winds that blow in an opposite direction in winter than in summer.
A. Causing
B. That cause
C. To cause
D. What causes
我选的A但答案是D,请讲解下这里为什么不能用现在分词?为什么用what causes? 谢谢

Answer 1

What causes seasonal rainfall is winds that blow in an opposite direction in winter than in summer.是这个句子的主干,两个逗号中间的内容通常是插入语,对句子主干内容进行相应补充说明,一般分析长句复杂句时,...