状语从句
所谓状语从句，是指用来说明主句行为发生的时间、原因、条件、地点、目的、结果及方式等。
1) 时间状语从句：记住以下连接词的意思和重点：
when / while / as
注意：while除了做时间状语的连接词外，还解释为虽然，而.
例如：He is very diligent, while she is very lazy.
before 在之前
until / not until注意：not until放在句首时，往往要求倒装
as soon as / once
immediately / instantly / directly 原本是副词，这里作连接词，表示一就，
例如： I knew I had made a mistake directly I had done it.
the moment / each time / every time / next time / the first time / the instant / the year原本是名词或副词，这里作连接词用。
hardly when / no soonerthan一就
注意：这是时间状语考试的重点句型，一是不要把两个句型中的when和than的搭配搞错了，二是要用倒装语序。
例如：
Hardly had I sat down when the telephone rang.
重点：在时间状语中，用一般时代替将来时。
例如：
Well start as soon as the leader ______.
A.comes B.is comingC.will come D.came
根据英语时态一致性原则，主句与从句的时态应一致，答案似乎应该是B或C，但是正确答案是A，因为在时间状语中，用一般时代替将来时。将上句改为过去时，道理也一样：
He said we would start as soon as the leader _____.
A.came B.was coming C.would come D.comes
答案应为A。