引导时间状语从句的从属连词（词组）有：1. When, as , while, before, after, till, until, since, as soon as, once, whenever, , , 等。
2. Every time, the first/ next time, the moment/ minute/ instant, the day等词引导时间状语从句。
3. Immediately, directly, instantly常作连词，引导时间状语从句，词义同as soon as, the moment.
1.定语从句的省略
在限制性定语从句中，常可省略作宾语的关系代词；在way（方式），time和moment后的that也常被省略；当先行词是time， reason，place时，作状语的关系代词when，why，where也可以省略。
2.状语从句中的省略
A. 在when，while，whenever，till， as soon as， if，unless，as if，though，as，whether等引导的状语从句中，若谓语有be且主语又跟主句主语相同或从句主语是it时，则从句的主语和be常被省略，结构常为：
连词（though，whether，when）+形容词；连词（whether， as if，while）+介词短语；连词（when，while，though）+现在分词；连词（when，if，even if, unless, once, until, than, as)+过去分词；连词（as if, as though)+动词不定式
B.虚拟条件句常可以省略if，将were，should，had提前。
练习：
1. He smiled politely ___ Mary apologized for her drunken friends.
A. as B. if C. unless D. though
2. You must learn to consult your feelings and your reason ___ you reach any decision.
A. although B. before C. becau D. unless
3. I have heard a lot of good things about you ___ I came back from abroad.
A. since B. until C. before D. when
4. ___ I have to give a speech, I get extremely nervous before I start.
A. Whatever B. Whenever C. Whoever D. However
5. I had hardly got
