现在完成时表示1)过去发生或已经完成的动作或存在的状态对现在造成的影响或结果.(即它的"完成用法")e.g. I have just cleaned the classroom. 2)过去已经开始，一直持续到现在的动作或状态。注意：此时动作可能还要继续。(即它的"未完成用法")。 E.g. He has lived in Beijing for ten years.
它的否定句是在have/has后边加not，变一般疑问句是把have/has提前。E.g. I have ridden a horse. I have not ridden a horse. Have you ridden a horse?
它的时间状语通常为already, just, yet, ever, never, before等。另外还可和since+表过去的时间点，for+时间段连用。
例：He taken (take) the medicine before.
解析：have/has 为助动词，起构成时态的作用，是不能省略的。我们可以这样记：“现在完成时态中，have/has 不可缺。”
例：I has never heard (hear) of that before.
例：She has left (离开) for 2 hours.
答案：has been away
解析：在肯定句中，与since或for引出的时间状语连用的是延续性动词，不能是短暂性动词，但在否定句中短暂性动词也是可以的。E.g. I haven't bought clothes for one year. 在此题中leave是短暂性动词，不能与for+时间段连用，须把它改成相应的延续性动词。如stop be over等。此题中leave要改成be away。这两种词的转换是学习现在完成时需要注意的。
1 You have _____ a tall young man.
A grown B grown into C grown us D grown up
2 He has ____ the watch for a year.
A buy B bought C have D had
3 Has your brother _____ the dog?
A kept in B fed C fed on D kept on
4I _____this book for two weeks, I have to return it now.
A borrowed B have borrowed C kept D have kept
5 Have you ever _____to the Great Wall? It's very beautiful.
A gone B been C went D go
6 Her brother _____the Party since 1978.
A joined B has joined C has been in D was in
7 The Greens _____many places of interest since they came to China.
A will visit B visited C have visited D visit
8 I'm sorry, I ____ your name.
A had forgotten B forgot C have forgotten D forgotten
9 The bookshop _____ for eight years.
A has been open B has been opened Chas opened D has open
10 We have all the paper so we need to buy some.
A used up B made of C filled with D hunted for
11 The flower I ____grown up.
A planted has B planted have C has planted D have planted
答案：1B 2 D 3 B 4D 5 B 6 C 7 C 8 C 9 A 10 A 11 A
1 Have you ever ______(take) a train?
2 It _________(be ) more than three years since Jim ______(leave) here.
3 Have you _____(make)friends with your new classmates yet?
4 I _______(have) my lunch and I'm not hungry now.
5 Jim has never seen a panda, _____he?
6 We ______(be) good friends since we met at school.
7 We can't find him anywhere. Perhaps he______(go) home.
8 He _____(read) the book before.
9 Mr. Green _____(teach) us a lot about social studies since September.
10 I _____never____ (meet) her sister before.
答案：1 taken 2 has been, left 3made 4 have had 5 has 6 have been 7 has gone 8 has read 9 has taught 10 have met
四、have been to与 have gone to 易弄混
I have gone to Beijing.
答案：I have been to Beijing.
解析："have been to+地点" 是表示曾去过某地，但此刻不在那儿(即在说话的地方)。而"have gone to+地点" 是表示去某地了，此刻在路上或已经到了那个地方(即不在说话的地方)。注意：这两个句式后接副词时，需省to。E.g. He has gone there.
例：I have already finished my homework.(变一般疑问句)
Have you already finished your homework?
答案： Have you finished your homework yet?
例：I'll go with you when I finish(finish) my homework.