I answered the letter yesterday.

When I saw him, he has finished the letter .

I went to the post office to mail the letters.（英译中)

He let a week go by before answering the letter.（英译中)

I found a letter lying on the floor when I came into the classroom.（)

I have much business that has ____ my answering your letter.

That the letter is found and answered so many years later is a（n)______to all the people.