There _______ two books and a pen on the desk.

 — Each of the students, working hard at their lessons, ______the book.  — So have I.

I, who ______ your close friend, will try my best to help you out of trouble.

The number of the students in our school _____ than that in theirs.

We collected a lot of books to get the necessary information but only half _________helpful, so we failed to finish the work.