A.I have done or I did
现在完成时涉及过去和现在 The plane has just landed.
一般过去时涉及过去 ,已经结束的某个时间。 The plane landed ten minutes ago.
B.I've done it. I did it yesterday.
We've bought a new car.
On,have you ? What sort?
An Adagio.We bought it last week.
C含有for，since和last的结构
现在完成时，可以用for表示某事持续一段时间，用since表示某事从过去开始一直在延续
We haven't had a party for ages.
一般过去时，可以用since表示某事发生好久了，可以用the last time表示某事何时最后一次发生
It's ages since we last had a party.
