第一节 单项填空（共15小题；每小题1分，满分15分）
21．- Can you read the sign，sir? No smoking allowed in the lift!
- ．
A．Never mind B．Don’t mention it
C．Sure．I don’t smoke D ．Pardon me
22. After two years' research, we now have a _______ better understanding of the disease.
A. very B. far C. fairly D. quite
23. At the beginning of class, the noise of desks _______could be heard outside the classroom.
A. opened and closed B. to be opened and closed
C. being opened and closed D. to open and close
