大全790，没人问过

1.        The number of mountain gorillas is declining with such rapidity that the population is one-half in the twenty years between a count made by George Schaller in 1960 and the one made by Dian Fossey in 1980.

(A) with such rapidity that the population is one-half

(B) with such rapidity that the population was one-half

(C) so rapidly the population divided in half

(D) so rapidly that the population was halved（D）

(E) in such rapidity that the population is halved

D    was halved和double做动词用法一样吗，记得double做动词是主动的，这里怎么是被动？

顶

时态:没有问题，指的发生在过去的事情。

语态：只能使用被动，因为halve是及物动词，如果主动则句子缺宾语。