题目内容：

Mark did not know what he should do to help him.怎样改为同义句

优质解答

Mark did not know how to help him.

追问：

不对呀，填空是Mark did not know ______ _______ ______to help him.

追答：

what should do应该可以，因为主语相同，可省略从句中的主语he