really have to leave during class, you’d better leave____ the back door.

He was encouraged to start again _________ he had failed.

It____be thepostman at the door. It’s only six o’clock.[ ]

What do you think of our school, Thomas? — Terrific! It is a school _______ everybody tries his best to improve himself and keep up with others.

______ is surprising to us is that Tom, for _______ English was once boring, can speak English fluently as though he were a native speaker.