中国的海域1、现在完成时态表示过去发生的动作对现在造成的影响或结果。本时态标志词：
already （已经，用于肯定句中，放在have /has之后或句尾）；
yet （仍然，还，用于疑问句或否定句的句尾）
just（刚刚，放在have /has之后）；
before（以前，放在句尾）；
ever（曾经，放在have /has之后）
never （从没有，在have /has之后）例句：
(1)Our teacher has just left.
车间流水线
(2)We have studied English already.
(3)I have not finished the homework yet.
(4)He has never been to Beijing before.
2、某个动作从过去已经开始，一直持续到现在，还有可能持续到将来.动作的持续性要通过一段时间来表示一段时间的表达方法有两种:
for: +一段时间for a year for two weeks for three years
Since +过去的某一时刻, since nine since last week Since +一般过去时态的时间状语从句since you came since you got home.
行转列注意：结束性动词不能和表示一段时间的时间状语连用，但是它们可以转换成相应的延续性动词：
（1）直接用延续性动词buy–have；catch(get) a cold –have a cold；borrow—keep；become—be；put on—wear
（2）转换成be+名词join the army –be a soldier；join the Party –be a Party member；go to school–be a student
彪学长（3）转换成be+形容词或副词die—be dead；finish —be over；begin —be on；leave—be away ；fall sleep —be asleep close —be closed come to/ go to/arrive at(in)+某地—be in(at) +某地
（4）转换成be+介词短语go to school–be in school ；get up_ be up；
3、现在完成时态常见标志词：
1. already（已经）, just（刚刚）, never（从未/从没有）, ever（曾经）, yet （仍然/还）, before（以前）（句尾时）。
2. since+点时刻或从句; for+段时间; how long（疑问句中用来提问since/for短语的）
3. so far；till now；by now（到目前为止；迄今）
4. recently近来in the past/last+段时间在过去的几年中
5. once(一次)，twice, three(four…) times
6. It is the+最高级+n.+ (that) sb.have ever done 例：What’s the best gift you have ever received? 你曾收到的最好礼物是什么?
4、现在完成时句型举例：
1. Have you ever been to an amusement park? 你曾经去过游乐园吗?Yes, I have./ No, I haven’t.
2. I have never been there. Me neither=Neither have I. 我也没有.
3. Where is he? He has gone to the Beijing.
4. How long has he been in Beijing? （不能用come/arrive）
5. I’ve never been to an aquarium. 我从没去过水族馆.
6. I have been a student here for a year. 我成为这的学生有一年了. （不能用become）=I became a student here a year ago.辛格顿船长
7. He has been dead for two years.（不能用die）=he died two years ago.沙漠狐狸
8. I have been a teacher since ten years ago(for ten years.) （不能用become）
9. I have just/ever/already/never seen the movie. Have you ever heard of the man before