大学英语四级考试涉及的语法知识点多、涉及面宽，对不少考生来说都是一个难题。希望通过本专题的学习，考生能对四级语法有更全面的掌握！
状语从句省略
1、 主句和从句的主语保持一致，称为分词作状语。
(1)条件：状语从句，前后主语一致
(2)形式：分词作状语在句首+分词作状语在句后
(3)省略方式：关系词(可保留)+动词形式变化(-ing/-ed)
在状语从句中，若前后主从句主语一致，则省略从句的主语，将后面的动词发生形式上的变化， 主动语态变成ing形式，若是被动语态，则变为ed 形式。
2、 若前后主语不一致，则称作独立主格结构。
一、用作时间状语
1. 典型例句
When [As soon as] the mouse saw the cat, it ran off.
Seeing the cat, the mouse ran off. 见到猫，老鼠就跑了。
真题示例：When _______ different cultures, we often pay attention only to the differences without noticing the many similarities. (2006浙江卷)
A. compared B. being compared C. comparing D. having compared
二、用作原因状语
1. 典型例句
As she was very weak, she couldn’t move.
Because she was much discouraged, she moved on to London.
(1) ______ with so much trouble, we failed to complete the task on time. (2006四川卷)
A. Faced B. Face C. Facing D. To face
三、用作条件状语
1. 典型例句
If you work hard, you will succeed.
If we are united, we stand; if we are divided, we fall.
If we had been given more time, we could have done it better.
四、用作让步状语
1. 典型例句
Although living miles away, he attended the course. 虽然住在几英里以外，他仍去上课。
五、用作伴随状语
1. 典型例句
He sat in the chair reading a newspaper. 他坐在椅子上看报。
He came in, followed by his wife. 他走了进来，后面跟着他的妻子。
My cousin came to see me from the country, ______ me a full basket of fresh fruits.
A. brought B. bringing C. to bring D. had brought
We often provide our children with toys, footballs or basketballs, _____ that all children like these things.
A. thinking B. think C. to think D. thought
六、用作方式状语
1. 典型例句
He came as we expected.
He came as he was expected.
I'm returning your letter as requested. 我按要求给你退信。
七、用作结果状语
1. 典型例句
He fired and killed one of the passers-by.
He fired, killing one of the passers-by. 他开枪了，打死了一个过路人。
He died and left his wife with five children.
He died, leaving his wife with five children. 他死了，留下他妻子和五个孩子。
He glanced over at her, ______ that though she was tiny, she seemed very well put together.
A. noting B. noted C. to note D. having noted
Speeding off in a stolen car, the thief thinks he has got a great catch. But he is in for an unwelcome surprise. (06.6旧)
_____ by the superstars on television, the young athletes trained hard and played intensely.
A) Imitated B) Imposed C) Insured D) Inspired (06.6旧)
When applying for a job, one usually has to submit a resume or curriculum vitae (CV). Alarmed by this state of _____ , the Japan Automobile Manufacturers Association (JAMA) proceeded a comprehensive study of the market in 2006. (09.完形)
A) mess B) boom C) growth D) decay
Sticking to the low end of the government estimates, the National Resources Defence Council says there were maybe no more than 3.2 billion barrels of economically recoverable oil in the coastal plain of the ANWR, a drop in the bucket that would do virutally nothing to ease America's energy problems..