such heavy pollution already, it may now be too late to clean up the river.
A. Having suffered
B. Suffering
C. To suffer
D. Suffered
网友回答
(答案→)A. Having suffered
B. Suffering
C. To suffer
D. Suffered
解析:本题考查分词短语作状语的用法。分词作状语,其逻辑主语必须是句子的主语,而本句的主语看似是it,其实它为形式主语,真正的主语为不定式,而不定式省略了逻辑主语for people,所以应用现在分词,又因already,应用完成时。