He didn't do his homework yesterday 为什么do是原型.不是疑问句吖——.

didn't 的原形是do not , do为助动词,助动词后面都是跟动词原形.
do homework是做作业的意思.
He didn't do his homework yesterday.
他昨天没有做作业.

那把didn't 拆了吧
He did not do his homework yesterday.
do的过去式是did,因为do作为助动词时,后面加动词原形,所以跟在did后面的动词也是用原形.
再问： 再问一下。I went to your home，but you weren‘t in you不是单数吗。为什么不用wasn’t?还是有别的原因。求解。、最好快点。或者能留个Q不--。偶加分。
再答： you 后面一定是跟are，不论是代表“你”或“你们”意思，不能跟is。没有you is 的用法。 这是英语固定的搭配。