问题补充:
单选题Rarespeciesintheworld,______byhundredseveryyear,mustbejointlypreservedbyallcountries,orhumanswillencounterecologicaldisasterinthenearfuture.A.disappearedB.disappearingC.disappearD.having disappeared
答案:
B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。