3、当从句的动作发生于主句动作之前，只能用when 引导这个从句，不可用as 或 while。

例如：When you have finished your work, you may have a rest.

2、Not until …在句首，主句用倒装。

例如：Not until the early years of the 19th century did man know what heat is.

直到19 世纪初，人类才知道热能是什么。

Not until I began to work did I realize how much time I had wasted.

直到我开始工作，我才认识到了我已蹉跎了几多岁月。

1、如果hardly, scarcely 或no sooner等置于句首，句子必须用倒装结构：

例如：Hardly / Scarcely had I got home when it began to rain.

No sooner had I got home than it began to rain.

由because , since , as , for , now that 等引导

例如：As the weather was fine ,we decided to climb the mountain.

第二节 实战演练

由连接词though, although, even if , even though, as 等引导。但要注意从句用了though主句就不能用but。

例如：Although it’s raining ,they are still working in the field.

Boy as he is , he knows what is the right thing to do.

引导方式状语从句的从属连词有as，(just)as…so, as if (though). As引导的方式状语从句通常位于句首。As在句中带有比喻的含义，意思是“正如……， 就像…… ”。

例如：It looks as if the whether may clear up very soon.

　　　 As water is to fish so air is to man.

由that, so that…或such…that引导。

例如：It is such a difficult problem that nobody can work it out.

由so that… , in order that , lest , in case , for fear that 等引导的从句的谓语动词常与can , may , could , might , should 等情态动词连用。

例如：Take an umbrella in case it should rain.

Ask him to hurry up with these letters in order that I can sign them.

由连接词as…as、than、not so…as…等引导。

例如：He speaks English much better than any other student in his class.

由连接词if, as long as, on condition that , supposing 等引导。如果主句用一般将来时，从句应用一般现在时。

例如：As long as you keep on trying , you’ll certainly succeed.

We will let you use the room on condition that you keep it clean and tidy.