现在完成时适用于以下情况：

1.表示过去发生或已经完成的某一动作对现在造成的影响或结果。

举个例子：

I have just posted a letter.我刚把信邮寄了。

2.表示过去已经开始，持续到现在（也许还会继续进行下去）的动作或状态；常和表示一段时间的状语，如：today，these days ,since …, for…, this month, now等连用。

举个例子：

I have studied English for two years.我学习英语已经两年了。

They have been in Beijing since 1949.他们从1949年起就住在北京。

3.现在完成时的构成： have/has +动词的过去分词

练习：

1.——What a nice bike! How long ( ) you ( ) it?

——Just two weeks!

A. Will; buy B. did; buy C. are; having D. have; had

2.——May I go to play tennis with you, Dad?

——( ) you ( ) your composition yet?

A. Are; finishing B. Did; finish C. Will; finish D. Have ; finished

3.You don’t need to describe her, I ( ) her several times.

A. had met B. have met C. met D. meet

4.——I’m sorry to keep you waiting.

——Oh, not at all, I( ) here only a few minutes.

A. Have been B. had been C. was D. will be

5.——Have you ( ) been to our town before?

——No, it’s the first time I ( ) here.

A. even; come B. even; have come C. ever; come D. ever; have come

参考答案：

1.D 考察现在完成时的用法，buy是非延续性动词，因题中有表示延续意义的时间how long,所以应把buy转换成have.

2.D yet是现在完成时一般疑问句和否定句的常用表示。

3.B 本题后句强调对现在的影响，我知道她的模样，你不用描述。Several times告知为反复发生的动作，因此用现在完成时。

4.A 等待的动作由过去开始，持续到现在，应用现在完成时。

5.D ever意为曾经或无论何时，反义词为never，次两句常用语完成时。如： This is the largest fish I have ever seen. It is/was the first time +that clause 的句型中，从句要用完成时。