This is __________ ruler. That’s __________ eraser.A. a, a B. an, an C. a, an
—Look! The boy in the white shirt ___be Tom. --It ____be him. I saw him enter the library just now.
Students should do everything they can __their study.
If you are a little careful, I think you can _____the problem.
Joan writes ____than she did 2 years ago.
—The pollution problem here seems to get more and more serious. --Yes. Something_____about it.