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Since then, it has become part of my life.
现在完成时(三)
当表示动作已经充成并对现在有一定影响时,我们一般用现在充成时。同时,可分别 用just, already或yet加以强调或说明。
其结构也是:
have / has +动词的过去分词.
常用的时间状语有:
already, just, 一般置于have/has 之后,用于肯定句中;在否定句中则要用yet 表示“还,未”。
Grammar
for 和 since 在现在完成时中的应用
for与since都能与现在完成时连用,但区别较大:
(1)for后须接“时间段”
He has studied English for five years.
他学英语5年了。
(2)since后须接“时间点”
He has studied English since 1999.
他从1999年开始学英语。
(3)二者可以转换
for + 一段时间 = since + 一段时间 + ago
He has been here for five weeks.
= He has been here since five weeks ago.
他到这儿已经有五个星期了。
如:
He has taught here since he came to China.
自从他来到中国就在这儿教书。
We have been friends since we met in school.
我们从在学校见面起就成为了好朋友。
(4) since能引导时间状语从句(主句用现在完成时,从句用一般过去时),而for则不能。
(5)现在完成时常用句型:
①It is (has been) +时间段+ since +时间状语或从句
It is four days since last Friday.