肯定句：主语+have/has+过去分词
否定句：主语+have/has not +过去分词
疑问句：Have/Has+主语+过去分词
7. 现在完成时
(1) 现在完成时的句型结构
①肯定句：主语+ have/has+ 过去分词
②否定句：主语+ have/has+ not+过去分词
③疑问句：Have/Has +主语+过去分词
(2) 现在完成时的用法
①表示到目前为止曾经有过的或未曾有过的经历和体验.常和never, ever, several times等连用.
如：
I’ve never been to Africa.
Have you ever been to Tokyo?
I’ve been there three times.
②. 表示某动作从过去开始,现在刚刚完成,对现在有一定的影响.常与just, already, yet, so far等词语连用.
如：
He has just finished his new book.
注意：just now用于过去时.
③.表示某动作从过去开始,一直持续到现在,可能还会持续下去.通常与x0bfor或since连用.
如：I have lived in Qingdao for 6 x0byears. /since 6 years ago/since 2003/x0bsince I came to this city.
It is/has been …+ since….
It’s been seven years since we last saw each other.
It’s six years since he was a teacher.
注意:for+一段时间,since后接一个过去的时间点或一般过去时的句子.
④ 在表将来的时间状语和条件状语从句中代替将来完成时.
如：
You can go home when you have x0bfinished your work.
比较：You can go home when you x0bfinish your work.
(3) 过去分词的构成
① 一般情况下在动词词尾后直接加-ed.
如：
listen-listened, talk-talked
② 以不发音的字母e结尾的动词,直接加-d.
如：
live-lived, hope-hoped
③ 以辅音字母加y接尾的动词,y变i,再加-ed.
如：
worry-worried, hurry-hurried
④ 以重读闭音节结尾,且结尾只有一个辅音字母的动词,双写辅音字母,再加-ed.
如：
drop-dropped, plan-planned, stop-stopped
⑤ 不规则变化
如：
cut-cut-cut, come-came-come
begin-began-begun, lend-lent-lent
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