21. _________still happens that some people don’t inform the police of their archaeological discoveries, because they doubt whether their finds are________ interest and value to archaeologist.

A. It; of                B. This; of

C. It; with            D. That; with

22. Great scientists are enormously curious and _________ doubt things we take for granted.

A. are used to              B. tend to

C. object to                  D. used to