1.They(already know)_have already known__one each other.
2.I should(know)__know__their trouble.
3.yesterday(be)__was__the first day of the new-school year.
4.we ought to(help)_have helped___our parents yesterday.
5.My mother often(watch)_watches___TV in the bed room.
6.she(cut)_is cutting__the lawn in the garden now.
7.She is fond of(read)__reading_books very much.
8.If peter(have)__has_time.She'll go to science club.
9.The young boy is interseted in(play)__playing__tennis.
10.I knocked the door while he(read)_was reading__a book.