【编者按】2011年学位外语考试在即，为了帮助大家复习，威廉希尔app 的小编特别整理了学位英语考试英语语法重点复习，供大家参考。
情态动词
情态动词用来表示能力、允许、许诺、可能、劝告、意愿等概念或态度，无人称变化，在句子中和动词原形一起构成谓语。着重测验情态动词接完成时的用法。 情态动词用来表示能力、允许、许诺、可能、劝告、意愿等概念或态度，无人称变化，在句子中和动词原形一起构成谓语。着重测验情态动词接完成时的用法。
must + have done 表示对过去发生的事情的有把握的猜测。
58、I believe he _____ an accident， otherwise he would have arrived on time. (D，01)
A. would have had B. could have had C. should have had D. must have had
47. Something must have happened on their way here. Or they _________by now. (02)
A. should have arrived B. should arrive C. would have arrived D. would arrive
答：C.第一句是must+have +过去分词的结构，表示对过去事实的推测。The road is wet. It must have rained last night.路是湿的，昨晚上肯定下雨了。因此我们可以推断：这是一个和过去的事实相反的虚拟语气。should +have +过去分词的结构，表示对过去动作的责备、批评。如：You should have gone over your lessons.你应当把功课复习好的。但是此句只是一个表示和过去的事实相反的虚拟句子，并没有责备的意思。本句意思：路上肯定出事了，否则他们现在已经到了。因此正确答案应是C.
35. Since this road is wet and slippery this morning， it last night. (C，0411)
A. must rain B. was raining C. must have rained D. may rain
may + have done 对过去发生的事情的较有把握的猜测，“也许”
22. I can‘t find the recorder in the room. It C may have been taken by somebody.
( 0311)
二、should (ought to) + have done 含有对过去的动作的责备、批评意思
肯定表示应该做的事情而没有做
26、I‘m sorry I couldn’t get in touch with him before he left， I ____ him earlier. (2000)
A. had a telephone B. have phoned C. should have phoned D. should be phoned
36、You ought to B to have reported the matter to the manager the day before yesterday.
否定式表示不该做的事情做了
They should not have left so soon. 他们不应该这么早就走的
She was very unhappy. You ought not to have hurt her feeling.
她当时够难受了你不应该再伤害她
三、would (not) have done
表示过去没有完成的动作，多和虚拟语气连用，不含批评意思
45. Mary said to me， “Had I seen your bag， I it to you.” (D，0404)
A. will return B. must return C. could return D. would have returned
四、could + have done
表示过去存在的某种可能性，但这种可能性由于客观条件限制没能实现。表示对过去能做而未做的事情感到惋惜，遗憾。
You could have made a more detailed plan. 你本可以做出更详尽的计划。
He could have joined us， but he didn‘t get our invitation in time.
他本来能够参加我们的，但是他没有收到我们的请贴。