2015年成人英语三级考试考点：情态动词

　　学位英语考试中重点语法知识主要包括：时态、语态、情态动词、虚拟语气、非谓语动词、从句、倒装句、强调句、主谓一致等。今天主要学习有关情态动词的语法知识点。情态动词没有人称的变化。除了ought后接to do，其它的情态动词一般和动词原形一起构成谓语。

　　1.must+现在完成时结构：这一结构表示对过去一个动作比较有把握的猜测。

　　例：I believe he _____ an accident, otherwise he would have arrived on time.

　　A. would have had B. could have had

　　C. should have had D. must have had

　　答案为D。

　　2.情态动词无人称变化，在句子中和动词原形一起组成谓语。只有ought后面接to do。

　　情态动词后接完成时的用法:情态动词用来表示能力、允许、许诺、可能、必须、劝告、意愿等概念或态度。

　　3.could+现在完成时，表示本来能做的事情而没有做。

　　例：Mary _____ that coat, but she chose to lend the money to a needy neighbour.

　　A. could have bought B. must have bought

　　C. can buy D. could buy

　　答案为A。玛丽本来可以买那件大衣的，但是她把钱借给一个更急需的邻居了。

　　4.should (ought to )have done用来表示本来应该做却没有做的事情。

　　例：I’m sorry I couldn’t get in touch with him before he left, I _____ him earlier.

　　A. had a telephone B. have phoned

　　C. should have phoned D. should be phoned

　　答案是C。中文意思是“我很抱歉我没能在他走之前和他联系上，我本应早点儿给他打电话的。”