21. —I want to know if I__________ smoke here.

—No, you _________.Could you see the sign “NO SMOKING” there?

A. can; needn’t             B. must; can’t        C. shall; won’t              D. may; mustn’t

22. Children’s curiosity may _____________ many useful inventions.

A. lead to           B. take place      C. gather in         D. bring away