A.I have done or I did
現在完成時涉及過去和現在 The plane has just landed.
一般過去時涉及過去 ,已經結束的某個時間。 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的結構
現在完成時，可以用for表示某事持續一段時間，用since表示某事從過去開始一直在延續
We haven't had a party for ages.
一般過去時，可以用since表示某事發生好久了，可以用the last time表示某事何時最後一次發生
It's ages since we last had a party.