状语从句和主句的时态呼应
修饰主句谓语动词的句子是初中阶段要求掌握的状语从句内容。
说明主句动作发生的时间、
地点、条件、原因、比较、结果、目的和让步等，这样的从句叫状语从句。
状语从句的重点和考点是：
1）主句和从句的连接词，
2）主句和从句的谓语动词的时态呼应（相互关系）
3）时间状语从句和条件状语从句的谓语动词遵循主将从现规则。
概念：在复合句中，由时间连接词引导的状语从句叫做时间状语从句。
（在复合句中，要注意主句和从句的石头大多
要保持相对一致。）
要点：时间状语从句，由以下连词引导：
when, while, as, after, before, as soon as, since ,till/until ,by the time
在时间状语从句中，要注意时态一致。一般情况下主
句是将来时的时候，从句要用一般现在时。
1.when
当…的时候
Mozart started writing music when he was four years old.
2.while
当…时
He visited a lot of places while he was traveling.
3.as
在…的同时，一边…一边…
He smiled as he stood up.
4.after
在…..之后
He left the classroom after he had finished his homework the other day.
5.before
在….之前
Mr. Brown had worked in a bank for a year before he came here.
6.as soon as
一…就…
We began to work as soon as we got there.
I will write to you as soon as I get home.
7.since
自….以来，
到现在
表示自过去的一个时间起点到目前（说话时间）为止的一段持续时间，主句一般用现在完成时，从句用一般过去时。
Mr Green has taught in that school since he came to China three years ago.
(还可以作介词，本句从句还可以用短语：since three years ago)
8.till/ until
都可以作连词，连接时间状语，也可以作介词，与其他词构成介词短语，在句中作状语
They walked till /until it was dark.
Xiao Ming didn‟t leave home till/until his father came back.
9.by the time
到…为止（所在句子的主句应用完成时）
By the time he gets there, his father has already gone.
By the time I got to school, the class had already began.
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