注意事项 1)英语中不允许在though或although从句后用but。如果要强调前后两个部分的对比意义，可以在主句前加上yet或still。

Though he is young，yet he knows a lot.

虽然他年轻，但是他知道很多。

2)as引导让步状语从句，用倒装语序。

Young as he is,he knows a lot.

虽然他年轻，但是他知道很多。

3)当从句主语与主句主语一致，从句中谓语是be或者从句中主语是it，谓语是be的时候，可以将从句中的主语与be一起省略。如：

He didn't want to go there though (he was)invited.

虽然他受到过邀请，但是他不想去那儿。 【活学活用】 22.单项选择

1）Mr.Hall understands that_________maths has always been easy for him,it is not easy for the students.

A.unless　　B.since　　C.although　　D.when 

2）Don't be afraid of asking for help_________it is needed.

A.unless B.since C.although D.when

3）A good storyteller must be able to hold his listeners'curiosity_________he reaches the end.

A.when B.unless C.after D.until

4）-How far apart do they live?

-_________I know,they live in the same neighborhood.

A.As long as B.As far as C.As well as D.As often as 

5）He made a mistake,but then he corrected the situation_________it got worse.

A.until B.when C.before D.as 

6）_________I know the money is safe,I shall not worry about it.

A.Even though B.Unless C.As long as D.While 

7）-Dad,I've finished my assignment.

-Good,and_________you play or watch TV,you mustn't disturb me.

A.whenever B.whether C.whatever D.no matter

8）We were swimming in the lake_________suddenly the storm started.

A.when B.while C.until D.before

9）_________you think hard,you will have another possible way to keep away from the danger.

A.As far as B.If C.Just as D.Even if

10）_________，I have to put it away and focus my attention on study this week.

A.However the story is amusing B.No matter amusing the story is 

C.However amusing the story is D.No matter how the story is amusing

答案与解析：

1）C　Mr.Hall 懂得尽管数学对他来说向来容易，但对学生来说并不容易。

2）D　当需要帮助的时候，不要害怕向人求助。

3）D　句意为一个优秀的故事讲述者必须能够让听者的好奇心一直维持到他讲到故事的结尾处。

4）B　As far as I know"据我所知",是固定搭配。

5）C　他犯了一个错误，但没等形势恶化，他就扭转了局面。

6）C　只要我知道这笔钱是安全的话，我就不会为它担忧。as long as,只要。