________ 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
A
题中already是重要的信息，由此判断应使用完成式。
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________ 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
A
题中already是重要的信息，由此判断应使用完成式。
