doing exercise can make him relaxed可不可以是do exercise can make him relaxed?

题目

doing exercise can make him relaxed可不可以是do exercise can make him relaxed?
为什么“doing exercise can make him relaxed”中的doing exercise要用doing呢?

答案

这是动名词做主语,所以用的doing.
不能改成do,如果是do的话,句子就有两个谓语动词了,一个是do,一个是make.一套句子结构只能有一个谓语动词.