21.   —How about going climbing the mountain together this coming Sunday?

—_____, but I have to visit my grandparents with my father.

A. All right         B. Sounds great       C. No problem       D. No, I am very sorry

22. They haven’t seen each other for ten years, but they still keep in _____ contact with each other.

A. constant            B. Instant     C. content               D. consistent