今天小编为大家带来学位英语考试难点汇总，希望可以帮助大家高效复习，突破难关，提高学习效率，掌握更多知识点。
1.独立主格结构
独立分词结构：逻辑主语
1）She being my friend, I should have helped her. (人称代词逻辑主语用主格,逻辑主语与分词形成主谓关系用现在分词)
2）More time given, we should have done it much better. (逻辑主语与分词形成动宾关系（被动）用过去分词)
3）The students having done all the exercises, the teacher went on to explain the text.(强调分词发生的时间在主语动词的时间之前用现在分词的完成时)
4）Her money (having been )stolen, she couldn’t buy a plane ticket for her home. (同上，此句中being / having been常可省略)
5）There being no bus, we had to go back home on foot.( there being +逻辑主语是独立分词结构的一种特殊形式，表示存在，相当于一个状语)
2.情态动词与完成时连用
1）should +have+过去分词
表示过去“本应该……而实际未做”，暗示说话人对自己的责备、抱怨或遗憾的意思。否定结构为shouldn’t +have+过去分词，表示过去“本不应该……”而实际上做了的动作。
How I regretted the days when I had played and should have studied.
You shouldn’t have told anyone about it.
2）must + have +过去分词
表示对过去情况的推测，意为“一定， 想必，可能”。表示对过去情况的否定推测用“can’t (couldn’t) + have +过去分词”，不用“mustn’t + have +过去分词”，反意疑问句用have (has)。有明确表示过去时间的状语（before除外）时反意疑问句用did。
Since the ditch is full of water, it must have rained last night.
Joe can’t have left. I saw him just now.
The party couldn’t have been successful as you had hoped.
He must have finished his homework, hasn’t he?
He must have attended the meeting yesterday evening, didn’t he?
3）may (might) + have +过去分词
表示对过去情况的推测。用might + have +过去分词可以用于肯定句、否定句，但不用于疑问句。
In return I may have been able to teach you a little about medical technique.
Might he have been caught and killed?错误
4）can (could) + have+过去分词
表示对过去情况的推测。用于疑问句和否定句，不用于肯定句。
They can’t have lost themselves in the woods, because I drew a map to them.
Bill couldn’t have gone home this weekend. I saw him at the school ground this morning.
5）need + have +过去分词
表示过去“没有必要做”，有责备的意思。否定形式表示 “做了本不应该……”的事。
Need you have watched TV last night?
You needn’t have woken me up so early. It’s Sunday today.
6）would + have +过去分词
表示“本应该……，而未……”，would like to have +过去分词表示“过去希望做……但未……”。
We would have argued with you.
I would like to have seen the film.
3.关系代词as和which的区别
1）当非限制性定语从句放到主句的前面时，引导词只能用as，而不用which。
As is planned, we got there before eight.
2）As引导的非限制性定语从句指表示积极的意义，与主句是顺理成章，不能与之矛盾。若非限制性定语从句表示消极的意义，只用which。
He has succeeded in his career, as / which we all hope.
Her grandma died last week, which made her very sad.
3）当关系代词代替主句中的宾语从句或复合结构(如：宾+补；不定式短语；动词-ing形式短语等)时，一般只能用which,而不用as。
She told us that there was something wrong with her bike, which was true.
He asked her to help him with his English, which she did.
4）as在非限制性定语从句中，还常跟such连用。
There was a look of love in the teacher’s eyes, such as mothers have for their children.
4. as常用于一些固定结构中。
as is well known / as we all know众所周知as is said above正如上面所说
as might be imagined正如所想象的那样as is reported如报道所说
as has been pointed如所指出的那样as is expected正如所料