•Over the next few years, increasing demands on the Chattahoochee River, which flows into the Apalachicola River, could alter the saline content of Apalachicola Bay, which would rob the oysters there of their flavor, and to make them decrease in size, less distinctive, and less in demand.
A.
A. which would rob the oysters there of their flavor, and to make them decrease in size
B.B. and it would rob the oysters there of their flavor, make them smaller
C.C. and rob the oysters there of their flavor, making them decrease in size
D.D. robbing the oysters there of their flavor and making them smaller
E.E. robbing the oysters there of their flavor, and making them decrease in size
答案是D，伴随状语。但我想问，究竟象C这种结构, could do...., and do....是可以还是不可以的呢？是不是之前一定不能有逗号？
我当初选C的原因是觉得alter the saline content和rob the oysters是并列的动作，当然后面的decrease in size是不好的用法了。
谢谢