Rare species in the world, by hundreds every year, must be jointly preserved by all countries, or humans will encounter ecological disaster in the near future.
A. disappeared
B. disappearing
C. disappear
D. having disappeared
网友回答
A. disappeared
(答案→)B. disappearing
C. disappear
D. having disappeared
解析：考察非谓语动词用法。Rare species与disappear构成主动关系，所以使用现在分词。D项是完成式，本句没有体现出已经完成，故B正确。