21. Shangri-la, which is _______ happy home for the local people, is also ________ home to many birds and animals.
A. the; a B. /; / C. a; / D. /; a
22. Without facts, we cannot form a worthwhile opinion for we need to have a factual knowledge ________ our thinking.
A. which to base on B. which to be based on
C. on which to be based D. on which to base
