英语什么时候用单三形式、ing形式、过去式、将来式

单三形式 He does his homework everyday.一般的情况下.用单三.他每天都做作业ing形式 He is doing his homework now.现在正在做功课.用现在进行时过去式 He did his homework yesterday.以前的,就用过去时 .昨天做...