21．—Have you finished the plan?
—Yes, and it ______ by the experts for three times.
A. was being studied B. has studied
C. has been studied D. studied
22．—Hilary, I think I’ll just have some coffee for a change.
—______. The coffee I bought yesterday is in the cupboard.
A. Coffee would be better
B. Change it, please
C. So do I
D. Help yourself
