情态动词中应特别注意的典的型结构
They must be in the library, aren’t they? 他们一定还在图书馆，对吧?
They must have gone to the library, haven’t they? 他们一定去图书馆了，对吧?
They must have been to the library yesterday, didn’t they? 他们昨天一定去了图书馆，是不是?
Let me do it, will you? 让我来做，好么?Let me help you, may I? 请让我帮你，可以吗?
Don’t move, will you? 请你别动!
Go quickly, can you? 你能不能快点?
Let’s go for a walk, shall we? 咱们去散步，好么?
He used to live in the countryside, didn’t/usedn’t he? 他过去住在农村，对吧?