hadn't为什么，能解释么不是hadn't,是hadhis sister had a bad cough,she?为什么是didn'this sister had a bad cough,she?为什么是didn't刚才那倒正确答案是hadn't你能帮我解释一下两道题的区别么had better是不得不的意思，那么遵循反意疑问句的前否后肯原则那跟下面一道有什么区别his sister had a bad cough,she?为什么是didn't嗯为什么had在此处做实义动词，那么就要借助动词do，因为句子的时态是过去式，所以就是did，则遵循前否后肯原则就有didn't嗯，谢谢呵呵给个好评吧