有些时间, 地点, 条件, 方式, 让步或比较状语从句中, 如果从句主语与主句主语一致, 从句谓语又包含动词be, 就可以省略从句中的“主语+ be”部分。有时主语是it, 即使不与主句的主语相同, 也把“it + be”部分省去了。
1.连词+过去分词
1) Don’t speak until ( you are ) spoken to.
2) Once ( it is ) seen, it can never be forgotten.
3) Though _____C__ many times, David often drives after drinking.
A. to be warned B. having been warning C warned D. being warned.
4) He arrived home half an hour earlier than ( he had been ) expected.
2.连词+现在分词
1) Look out while ( you are ) crossing the street.
2) He stared at me as if seeing (see) me for the first time. 他盯着我看，就像第一次看见我似的。
3.连词+不定式
1) He cleared his throat as if to say (say) something. 他清了清嗓子，像要说什么似的。
4.连词+形容词 常见的有if necessary、if possible、when necessary等
1) ____Though cold______________ (虽然冷), he still wore a shirt.
2) Whenever _C__ possible, you should come and help. A. you are B. it C. / D. it was
5.连词+名词
1) When (_he was_____________________) still a boy of ten, he had to work day and night.
2) Once (_he was_____________________) a teacher, he now works in a government office.
6. 连词+介词短语
1) When (_I was_______) in trouble, I always turned to her for help.
2) In winter it is colder in Jinan than ( it is ) in Wuhan.
3) __C__ at school, Jill wrote her first detective novel.
A. During B. Since C. While D. In