Q27:
In Scotland, the number of wild salmon have been reduced because of uncontrolled deepsea
and costal netting, by pollution, and by various other threats to the fish’s habitat.

A. number of wild salmon have been reduced because of uncontrolled deep-sea and
coastal netting( 主谓不一致，不和by平行）
B. number of wild salmon is reduced because deep-sea and coastal netting is not
controlled(不平行，by 的逻辑意识不对）
C. numbers of wild salmon has been reduced because of uncontrolled deep-sea and
coastal netting（主谓不一致，不平行）
D. wild salmon’s numbers are reduced by deep-sea and coastal netting that is not
controlled（that 修饰对象错）
E. wild salmon’s numbers have been reduced by uncontrolled deep-sea and coastal
netting
Answer: E

不是太理解，我想选E的原因应该是by的并列，但有一点不太明白的是为什么E中使用

the wild samlmon's numbers 呢，这是什么用法？翻译起来怎么解释？

我觉得应该是the number of wild salmon has been reduced by... ,by..., and by...

此外这里用完成时也觉得没有什么必要，不过原句用了就算可以吧！