--that car must have cost a lot of money. --on,no._________ 请问否定回答用 it didn't 还是用 it can't. 不过记得是这样的 must have v-ed 否定形式为:can’t / couldn’t have v-ed,为什么又用it didn't 还是与can't/couldn't have 都可以?不太明白这点,请再指教