21. —Which of the two souvenirs do you like better?
— ______ blue one, of course. I think it's really ______ most instructive one.
A. A；the B. The；the C. The；a D. A；a
22. ______ is known to us is that tobacco contains nicotine and other harmful products, so you should give up smoking.
A. As B. It C. What D. Which
