这道题搞不清句内关系有没有！！！

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
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B选项冒号后面不应该是解释吗  为什么不是B呢？