问题描述: when did you do that 中do 为什么用原形不用过去式? 1个回答 分类:英语 2014-11-08 问题解答: 我来补答 you did that when这个是这句话的原来位置转换成问句 be动词或助动词要提前所以用did you do did就是do 的助动词形式比如:i had lunch at 8 o'clock转换:did you have lunch at . 展开全文阅读