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

不是很了解此题so的用法，NN们有三种解释：

（1）so 代替had a vocal tract ，此处的so倒装，全句为so Neanderthals were probably without language

（2）so 是副词（但是我并不理解so 作副词的用法）

（3）and so不是倒装, 而是有and连接, 用so表示的结果状语从句,在状语从句中主语相同,所以省略掉了!

还请NN们确定此处so正确的用法！

本人同意解释1，probaly without languange 是插入语，不要理解为were的标语