I don't know where he is.(否定句)Do you have a dictionary with you? (疑问句)I have been to Shanghai twice.(现在完成时)There will be a meeting tomorrow morning.(一般将来时)
如:can, may, must, would, should, need, dare, might, used to 等。She can speak English fluently.她能流利和说英语。You may take the book with you if you like.如果你喜欢,可以把这本书拿走。
Need we hand in our exercise-books before class?我们需要在上课前交练习本吗?
There must be a mistake.准是弄错了。You shouldn't do that.你不应该做那件事。