must表示推测的用法：
must be一定..... 对现在情况的推测.
must +动词原形（多为状态动词），表对现在情况的推测 must+be+doing ,表示对进行时的推测 must+have+done，表示对过去时的推测. →There must be a mistake There must be some books which could help me. She have worked all day,she must be tired . she must be working in the office now. I didn't hear the phone,I must have been alseep. 注意：否定推测用can't表示. →If tom didn't leave here until five o'clock,he can't be home yet. J ane's light is on,she must be at home ,she can't be out. That can't be the only way ,there must other ways of solving the problem.
It’s very late ,I have to work over.
Tom has to had said the truth.
练习：（注意肯定答语和否定答语）
Must I finish my homework now? yes ,you_____/ yes, you_______ No, you ______, No , you ___________
