一般将来时
I willsend the letter tomorrow.
The letter will be sent(by me) tomorrow.
we will play football tomorrow.
Football will be played (by us)tomorrow.
过去将来时
He said they would play football .
He said football would be played.
He said he would send the letter.
He said the letter will be sent(by him) tomorrow.
一般过去时
We played it yesterday.
It was played (by us)yesterday.
I sent the letter yesterday
Twe letter was sent (by me)yesterday.