结构形式：
肯定形式
主语+动词过去式+其它
例句：She came to help us in those day．
否定形式
主语+didn't+谓语动词原形+其它
①was/were+not；②在行为动词前加didn't，同时还原行为动词
例句：I didn't know you like coffee.
一般疑问句
①Did+主语+谓语动词原形+其它②Was/Were+主语+表语
例句：Did I do homework?
特殊疑问句
疑问词+did+主语+动词原形+其它
疑问词+was/were+物主代词/...'s+sth.
