21. _______ good knowledge of several languages is essential to _____ study of comparative literature because without it one can read books only in translation.

 A. A; the           B. A; /         C. The; the            D. /; the

22. Talking about buying computers, I prefer a computer less than 8,000 yuan to ______ over the amount.

 A. this               B. it            C. that                 D. one