for其后只能接表示" "的名词性短语，可用于多种时态，表示动作或状态持续时间段长短。

e.g. I have lived in this city for five years. 我在这座城市居住了5年了。

He usually sleeps for twelve hours every day. 他通常每天睡12个小时。

since 其后接表示" "的短语或从句（过去时），也可以接" "，常用于完成时态；还用于句型："It is +时间段+since+一般过去时的句子"。表示过去某个时间发生并持续到说话时的动作或状态。

e.g. It is two years since I came to China. 自从我到中国以来已经两年了。

She has worked here for five years. =She has worked here since five years ago.

她在这儿工作5年了。

六、达标测评

（一） 选择填空

1. -- ____ have you been married？

-- For twenty years.

A. How far B. How often C. How long D. How soon

2. If you sit in a chair ____ a long time, your back may begin to hurt.

A. at B. in C. on D. for

3. -- I often have hamburgers for lunch.

--You'd better not. It's bad for you ____ too much junk food.

A. eat B. to eat C. eating D. ate

4. --- When did you _______ the bike?

--- in 2012 . I have ______ it for two years.

A.buy ; bought B.have ; bought C. buy ; had D.bought; bought

5. --- How long has Mr.Green lived in Lanzhou?

--- He's lived here ______ 1998.

A. for B. since C. at D. On

　（二）用所给词的适当形式填空

1. Mr. Brown is the ______（make）of the food．

2.My father (work) in the middle school for 20 years.

3. These ______ (scarf) are Ann's and Alice's.

4.Ann has had the sweater since she （be）five years old．　

5.I think it's hard （ride）a horse. It's dangerous.