前两期我们介绍了现在完成时及其第一种用法，今天我们来学习第二种用法。
接触七：用法之二
表示过去已经开始，一直持续到现在的动作或状态。
因为表示的是持续的动作或状态，所以使用的动词通常是延续性动词，如be, stay, study, wait, keep, have 等；使用的时间状语通常由for或since 引导，但二者后接的词有所不同：
for后常跟一个时间段，指某个动作到现在为止已持续了多长时间，如for three years, for half an hour等。
since 作介词，后面可以接一个时间点，如since1980，也可以接“一段时间+ago”,如since three years ago, since two months ago等。since 还可用作连词，引导一个过去时态的时间状语从句。如：
We've known each other since we went to college.
非延续性动词不能直接和for 或since 连用，但我们可以找一个相应的延续性动词或动词短语来替换这些非延续性动词，如come→be, come to→be in / at, go out→ be out, leave→be away, begin / start→be on, stop→ be over，buy→ have, borrow→ keep, open→be open, close→be closed, join→be a member of, die→be dead, catch a cold→have a cold, get to know→know, become a teacher →be a teacher, fall asleep→be asleep, fall ill→ be ill等。
句型It is the first （second, third...) time that...的that从句中，谓语动词须用现在完成时，表示到说话时为止动作发生过几次。如：It is the first time that I have been here.
接触八：常用于现在完成时的时间状语
除了我们讲过的already, yet, still，just, ever, never, since短语和 for短语外，还有许多时间状语常用于现在完成时，我们要留心将它们和一般过去时的时间状语区分开来：
1. lately, recently是完成时的时间状语；just now 有a moment ago 之意，是过去时的时间状语。如：
Have you heard from your family lately/recently?
Did you see Joan just now?
2. in the past few years 意思是“过去几年来”，常用于完成时中；in the past意思是“在过去”，常用于过去时中。 如：
Great changes have taken place in my hometown in the past few years.
Where did you work in the past?
3. ever since then与from then on / after that 都有“打那以后”之意，但前者常用于完成时，而后两者常用于过去时。如：
She's lived here ever since then.
I didn't hear of Jim from then on/after that.
4. before 通常用于完成时；通常用于过去时。如：
I've never been to Japan before.
She went to Japan two years ago.
5. so far“到目前为止”， these days“这些天来”也是现在完成时常见的时间状语。如：
So far, no man has travelled farther than the moon.
What have you done these days?
