现在完成时
1. 现在完成时①表示过去已经完成，对现在有影响的, already 用于肯定句，助动词后、过去分词之前；yet用于否定、疑问句，常位于句末I have lost the key.② 表示动作或状态从过去开始，持续到现在，并有可能继续持续下去, 常与 for+一段时间；Since+时间点/ 从句Mr. Li has taught English for 10 years③ 副词在现在完成时中的用法⑴ just 表示刚刚，动作刚刚结束，助动词后、过去分词之前He has just come back from America⑵ever表示曾经，用于疑问和否定句，助动词后、过去分词之前Have you ever been to London?⑶never表示从来没有，常与before 连用，助动词后、过去分词之前⑷before 意思以前，表示过去不确定的某个时间，常位于句末。I have never heard of this singer before④延续性和非延续性动词在现在完成时中的用法⑴非延续性动词不能和一段时间连用I have left my hometown for 10 years.XXXXI have been away from my home town for 10 years.（2）否定句中非延续性动词能和一段时间连用（3）非延续动词与一段时间连用3个方法①将非延续动词转化为延续性动词非延续动词延续动词
buyhave
borrowkeep
openbe open
closebe closed
begin, startbe on
comebe here
go be there
finishbe over
diebe dead
catch coldhave a cold
put on wear
get upbe up
wake upbe awake
fall asleepbe asleep
losenot have
joinbe in
leavebe away
arrive/ reachbe
②时间状语改为过去时间，用一般过去式③ It is + 一段时间+since 从句（从句的谓语动词为非延续性动词）
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