本文从状语从句、一致性及错误的省略等方面讲解了有关省略句的大学英语四级语法基础知识，我们一起来看一下吧!
在以as, than, when, if, unless等引导的从句中的省略: 在有些状语从句中,如果谓语包含有动词be,主语又和主句的主语一致a),或者主语是it b),就常常可以把从句中的主语和谓语的一部分(特别是动词be)省略掉.
Look out for cars when crossing the street.
When taken according to the directions, the drug has no side effects.
While there he joined in voluntary labour on a project.
Although not yet six months old, she was able to walk without support.
If not well managed, irrigation can be harmful.
Though reduced in numbers, they gained in fighting capacity.
This viewpoint, however understandable, is wrong.
Enemies, once discovered, were tightly encircled and completely wiped out.
She hurriedly left the room as though/if angry.
She worked extremely hard though still rather poor in health.
Fill in the application as instructed.
Whenever known, such facts should be reported.
The documents will be returned as soon as signed.
He said that no acrobat could ever perform those daring feats unless trained very young.
Once having made a promise, you should keep it.
If necessary I’ll have the letter duplicated.
Fill in the blanks with articles where(ver) necessary.