比较since和for
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比较since和for
比较since和for
比较since和for
Since 用来说明动作起始时间,而for用来说明动作延续时间长度.
比如说 ：I have lived here for more than twenty years.
I have lived here since I was born..
My aunt has worked in a clinic since 1949.
Some new oilfields have been opened up since 1976.
I have known Xiao Li since she was a little girl.
My brother has been in the Youth League for two years.
I have not heard from my uncle for a long time.
但是也并非有for 作为时间状语的句子都用现在完成时.
I worked here for more than twenty years.
(我现在已不在这里工作.)
I have worked here for many years.
(现在我仍在这里工作.)
since+点时间 since+段时间+ago since+从句（一般过去时）
for+段时间
since常用于完成时态
for没有时态的限制
For和since的区别
区别一：For 后面使用时间段，since 后面使用时间点
区别二：Since 只能用在现在完成时态，For 最主要用在现在完成时和一般过去时
I has been a teacher for three years.
I has been a teacher since 1996.
I was a teacher fo...
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For和since的区别
区别一：For 后面使用时间段，since 后面使用时间点
区别二：Since 只能用在现在完成时态，For 最主要用在现在完成时和一般过去时
I has been a teacher for three years.
I has been a teacher since 1996.
I was a teacher for three years. 这种表达可以，for three years表示一段时间，was 表示过去做了三年，现在不是老师了
例： Since 1921 the budget of the United States became
A B
the primary responsibility of the president.
C D
分析：A错，应改 In. since一般要求主句用完成时态，而句中谓语动词为过去式，其时间状语应与之呼应，故改Since为In。
例：Adella Prentiss Hrghes served as manager of
A B C
the Cleveland Orchestra since fifteen years.
D
分析：D错，应改为for。since引导时间状语时，主句谓语动词为一般完成时；主句谓语动词为一般过去时要用介词for；而且一段时间用for, 而不是since。
52. In general, prawns lived in shallow coastal waters or in streams.
A B C D
自然现象和客观事实用一般现在时态，live
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