四六级

　　2017年上半年英语四六级成绩已经可以查询了，还不知道成绩的考生，可点击2017年6月四六级成绩查询入口!有任何问题可点击英语四六级成绩查询全攻略！

　　语法是英语学习的基础，坚实的语法是英语水平进阶的充分必要条件，比如说六级英语阅读中的长难句，句子中的单词都认识，但是却不明白句子的含义，这个时候，你就应该意识到，你差的不是词汇量，而是语法知识。今小编为大家整理了大学英语六级常用的语法知识，考生们要好好学习哦!

　　1、情态动词的完成式

　　1)must have done——表示对过去的事情较有把握的、肯定性的推测，常译为“一定，准是，肯定”，其否定形式是can’t/couldn’thave done，意为“决不可能，不太可能”。

　　e.g. Since the ditch is full of water, it must have rained last night.

　　2)should/ought to have done——表示过去应该做的却没有做，常含有后悔、责备、埋怨的口吻，意为“本应该”，“应该就好了”; e.g. With all the work finished, I should have gone to your birthday party last night.

　　3)shouldn’t/ought not to have done——表示过去不该做的事却给做了，也常含有责备、不满之意，意为“本不该”。

　　e.g. You shouldn’t have gone back to work yesterday without the doctor’s permission.

　　4)may/might have done——表示对过去的事情的推测，但不十分有把握，意为“可能，或许已经”。 e.g. A traffic accident happened yesterday and a driver may have been hurt.

　　5)could have done——表示过去有可能或有能力做某事，而实际未做、未能实现的事;有时也表示轻度批评，意为“本来可以，完全可以”。 e.g. The gas leakage could have been avoided if the gas company took immediate measures after the warning call.

　　6)needn’t have done——表示过去做了某事，但没有做的必要，意为“其实没有必要”。 e.g. I needn’t have bought all that wine——only three people came.

　　2、可作情态动词用的短语

　　would rather, would sooner, would (just) as soon, had rather, had better, had sooner, cannot but, may/might as well

　　[例1]You________ all those calculations! We have a computer to do that sort of thing.

　　A. needn’t have done B. must not have done

　　C. shouldn’t have done D. can’t have done

　　[例2]I ________to him because he phoned me shortly afterwards.

　　A. ought to have written B. must have written

　　C. couldn’t have written D. needn’t have written

　　[例3]You________ those letters. Why didn’t you

　　A. should post B. must have posted

　　C. should have posted D. ought to post

　　以上是小编为大家介绍的相关信息，希望对考生有所帮助，需要其他四六级备考信息的考生，可点击四六级备考资讯站查询。查询2017年上半年成绩的考生可以点击2017年6月四六级成绩查询入口查询。

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