英文問題！thx

Past Perfect
通常指兩件已經發生既事件的先後. For example: I had done my work (先) when my mom called me (後). 如果一句 I had done my work, 無咩意思, 即等於 I did my work.

Present Perfect
(1) 已經完成, 但是對現在有影響. For example, I have done my work so I can go anywhere (I am free now).

(2) 描述最近發生的事. For example, he has just done his work.

(3) 描述之前發生的事, 但是現在還有效. For example, I have been to USA. The student have gone to school. (They are still there.)

(4) 描述將來發生的事, 但要有 when, after, until, etc. For example, I will tell you when he has done his homework

i had done my work 是 past perfect , 是指已發生這件事之後有另一件事亦已發生了。如
i had done my work before i ate my lunch. 在我食完午餐之前我已經完全了工作。(在這個時候工作和午餐都已經成為過去）。
i have done my work, 是 present perfect. 是指已發生的事情。如
i have done my work and i am free 我已完全工作，現在很空閒。（工作是過去了，空閒還在進行中）