求助一道GWD！求指点！

Ashley0814

13. GWD31-Q13

Dolphins lack vocal cords, nevertheless creating sounds: a complicated system of whistles, Squeaks, moans, trills, and clicks are produced by sphincter muscles inside the blowhole.

A. nevertheless creating sounds: a complicated system of whistles, squeaks, moans, trills, and clicks are produced by

B. nevertheless creating sounds: they produce a complicated system of whistles, squeaks, moans, trills, and clicks with

C. but they do create sounds, producing a complicated system of whistles, squeaks, moans, trills, and clicks with

D. but they do create sounds, a complicated system of whistles, squeaks, moans, trills, and clicks being produced

E. but nevertheless creating sounds: a complicated system of whistles, squeaks, moans, trills, and clicks produced by

选项我选对了，就是C

但是我想知道A选项 are produced by的主语是不是有可能是clicks，有歧义？

D选项里，是不是 a complicated system不能当做同位语！

看了各位前辈们的总结，总算把comma + ving搞明白了，现在又出别的问题了。。。

求NN指点~~~

Ashley0814

给自己顶一下！d=====(￣▽￣*)b

Ashley0814

lululuna

这题关键在于句意的转折，but作为连词，连接lack...和 create两个动作，两个动作要平行的，所以AB是错的；
A的话，根据 主谓一致原则， 应该是is produced

Ashley0814

lululuna 发表于 2015-11-18 08:12
这题关键在于句意的转折，but作为连词，连接lack...和 create两个动作，两个动作要平行的，所以AB是错的；
...

谢谢NN！明白啦
就是发现自己看问题总是不够宏观，忽略掉整体的感觉，比如这题总体的转折！