have / has + P.P (过去分词)
1. 表示一件事，一个动作或一个情境，从过去某个时间点开始并持续进行到现在，常在句子中与表达时间的介系词for，since联用。
A. for后面需接一段时间: for ten minutes, for five days, for six months, for many years, for a long time
Julie has worked at the same bank for ten years.
Julie在同一家银行工作10年了 (现在还在那里工作)
I have known Joe for a long time.
我认识Joe很长一段时间了 (现在还认识)
Jean and Bill have lived in New York for many years.
Jean 和Bill住在纽约很多年了 (现在还住在那里)
B. since后面则接一个较具体的时间点 或过去式的副词子句 :since eight o’clock, since April, since 1997, since yesterday, since last week
I have been in class since ten o’clock this morning.
从今天早上10点我就在班上了 (现在还在)
Mia has learned French since 2008.
Mia从2008年就开始学英文了(现在还学)
Jerry and Mike have lived in Taipei since they were college students.
自从Jerry 和Mike是大学生就已经住在台北了(现在还住)
2. 强调一件已经完成的事或情境，或一个曾经历过，尝试过的经验，除了也和for，since，so far联用之外，副词ever, never, already, yet, still, just等也常与此形式联用。
Have you ever been to Canada ? No, I have never been there.
你曾去过加拿大吗？我从没去过
I have already seen that movie, but Jessie hasn’t seen it yet.
我已经看过那部电影了，但Jessie还没有
Ann started a letter to her parents last week, but she still hasn’t finished it.
Ann上星期开始写信给她的爸妈，但她至今仍旧还没完成
I have flown on an airplane many times.
我已经搭飞机很多次了
They have just heard some bad news.
他们刚听到一些坏消息
