现在完成时和过去时 (I have done and I did)
研究下面例句的场景：
Tom is looking for his key. He can’t find it.
He has lost his key. (现在完成时)
This means that he doesn’t have his key now.
过了10分钟后:
Now Tom has found his key. He has it now.
Has he lost his key? No, he has found it.
Did he lose his key? Yes, he did.
He lost his key (一般过去时)
but now he has found it. (现在完成时)
现在完成时(某事已经发生)是现在的时态。它告诉我们现在的情况。
一般过去时(发生的事情)只告诉我们关于过去的事情。如果有人说“Tom lost his key”，
我们不知道他现在是否有钥匙。我们只知道他在过去的某个时候失去了它。
比较现在完成时和一般过去时:
They’ve gone away. They’ll be back on Friday. (they are away now)
They went away, but I think they’re back at home now. (not They’ve gone away)
It has stopped raining now, so we don’t need the umbrella. (it isn’t raining now)
It stopped raining for a while, but now it’s raining again. (not It has stopped)
你可以用现在完成时来描述最近发生的事情:
I’ve repaired the washing machine. It’s working OK now.
‘Hannah has had a baby! It’s a boy.’ ‘That’s great news.’
通常，你也可以用一般过去时:
I repaired the washing machine. It’s working OK now.
用一般过去时(不是现在完成时)表示不是最近的或新的事情:
Mozart was a composer. He wrote more than 600 pieces of music.
(not has been … has written)
My mother grew up in Italy. (not has grown)
比较:
Somebody has invented a new type of washing machine.
Who invented the telephone? (not has invented)
我们用现在完成时来提供新的信息。但若持续谈论某个信息，我们通常使用一般过去时:
a: Ow! I’ve burnt myself.
b: How did you do that? (not have you done)
a: I picked up a hot dish. (not have picked)
a: Look! Somebody has spilt something on the sofa.
b: Well, it wasn’t me. I didn’t do it. (not hasn’t been … haven’t done)
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