may,might
表示请求和允许.might比 may语气更委婉,而不是过去式.否定回答时可用can’t 或mustn’t,表示“不可以,禁止”.
----Might/ May I smoke in this room?
---- No,you mustn’t.
---- May/Might I take this book out of the room?
---- Yes,you can.(No,you can’t / mustn’t.)
用May I...征徇对方许可时比较正式和客气,而用Can I...在口语中更常见.
can could
-----Can I go now?
---- Yes,you can./ No,you can’t.
---- Could I come to see you tomorrow?
---- Yes,you can.( No,I’m afraid not.)
must
---- Must we hand in our exercise books today?
---- Yes,you must.
---- No,you don’t have to / you needn’t.
need
作情态动词用时,常用于疑问句、否定句.在肯定句中一般用must,have to,ought to,should代替.
You needn’t come so early.
---- Need I finish the work today?
---- Yes,you must./ No,you needn’t.
would
表示请求、建议等,would表示委婉
Will / Would you pass me the ball,please?
yes,of course.