Rare species in the world, by hundreds every year, must be jointly preserved by all count

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.

解析：考查现在分词作状语。disappearing by hundreds every year做原因状语，disappearing的逻辑主语是Rare species，句意是在世界上，每年有上百种的珍稀动物消失，所以所有的国家必须联合起来保护它们，否则在不久的将来人们将遭遇生态上的灾难。Disappeared过去分词，表示已经完成的动作；having disappeared现在分词的完成式，表示谓语动词动作之前已经完成的动作；disappear动词作谓语，题干的谓语是must be，现在分词表示正在进行的动作，根据句意选B。

我明天再问问老师，叫他解释下这个问题