【基本用法】 过发现影--- 表示过去发生，对现在造成了影响。
e.g. Their parents have known the good news.They look excited.
过发持续--- 表示从过去开始，持续到现在的动作或状态。
e.g. I have learned English for 10 years.
经历 --- 表示曾经做过某事，或曾做过n次
e.g. I have seen the film Titannic twice.
【时间状语】 already, just, yet, since, since then, for, recently / lately,
so far = till / until now = up to now, in the last / past few years,
How longever, never, before, once, times
【重难点】 延续性与非延续性动词的用法
什么时候才必须用延续性动词？ 出现how long, for+时间段, since+时间点
非延续性动词转化
▲ 高频考点
borrow keep buy have
finish / end be over begin / start be on
open be open die be dead
join be in / be amember leave be away（from）
▲ 需了解记忆
get up be up fall asleep be asleep
fall ill be ill, lose be lost
become be return / come back / get back be back
close be closed catch / get a cold have a cold
arrive /come / go / move / reach /get to be in /at / be here /be there
【易错点】 in the past few years (不是 a few)
have been to, have gone to和have been in的区别
already与yet区别
since+时间点，for+时间段（since 3 years ago; for 3 years）
since 引导的从句要用一般过去时
It is /has been + 时间段 + since + 从句（一般过去时）
He came to our school in 2000, since then he has taught English here.