21. According to recent reports, one of the rare animals, ____ crocodile, is in ____ danger of dying out.
A. a; the B. 不填; a C. 不填; the D. the; 不填
22. In the botanical garden we can find a(n) _______ of plants that range from tall trees to small flowers.
A. species B. groups C. amount D. variety
23. This is a very special flower and it can _______ a strong sweet perfume at night.
A. give in B. give up C. give out D. give down
