13现在完成时＆一般过去时（1）

He has lost his key. 暗含：现在钥匙不在他那儿。
He lost his key. 暗含：现在不知是否已经找到。
He has found his key. 暗含：现在钥匙在他那儿。
谈论古人和已经故去的人的事，用一般过去时。
The Chinese invented printing.
How many plays did Shakespeare write?
Beethoven was a great composer.
比较：
Shakespeare wrote many plays.
My sister is a writer. She has written many books.
给出新信息用现在完成时,但继续谈论这个话题，用一般过去时。
A: Ow! I've burnt myself.
B:How did you do that?
A:I picked up a hot dish.
——
A:Look! Somebody has spilt milk on the carpet.
B:Well, it wasn't me. I didn't do it.
A:I wonder who it was then.