[求助][讨论]OG167的句子结构?

XDJM们看看 "a shortcoming" 是个啥成分? 另外, "so were probably without language" 是否省略了什么? 先谢!

正确答案是B.

167. Neanderthals had a vocal tract that resembled those of the apes and so were probably without language, a shortcoming that may explain why they were supplanted by our own species.

(A)  Neanderthals had a vocal tract that resembled those of the apes

(B)  Neanderthals had a vocal tract resembling an ape's

(C)  The vocal tracts of Neanderthals resembled an ape's

(D)  The Neanderthal's vocal tracts resembled the apes’

(E)   The vocal tracts of the Neanderthals resembled those of the apes

同位语从句，用一个概括性的词引导的。

省略了主语，或者说俩句子共趁一个主语。