He help his mother do housework.变过去式

题目

He help his mother do housework.变过去式
He help his mother do housework.怎么变过去式?

答案

He helped his mother do housework.
解析：help sb.do 是省to不定式,help后面的动词要跟原型,所以,过去时改为helped sb.do,不可以是help sb.did.