past perfect(had) is suitable here as vocal tract resemblence with that of ape's was a phenomenon which occured b4 Neanderthals were supplanted by our own species.

So IMO B as in A singular vocal tracts doesn't goes with "those".

Also in C and E vocal tract is wrongly made as subject.In D there is no antecedant for "they" as Neanderthal's is possessive

In the original sentence, Neanderthals does not agree with "vocal tract" -- the original sentence implies that all Neanderthals shared one vocal tract. So we need to look for something with Neanderthal/vocal tract or Neanderthals/vocal tracts. That eliminates A and B and D (although without that pesky apostrophe in Neanderthal's, I would probably go with D).

I think we can also eliminate C as well, since ape is singular but vocal tracts is plural (ie, if we extend the sentence, "The vocal tracts of Neanderthals resembled an ape's vocal tracts" which is incorrect)

That leaves us with E, which is awkward, but I think is technically correct.

You know actually, rethinking this (it's been bugging me) it can't be E since that would indicate that vocal tracts were without language.

I guess I would go with B then, but I'm not sure why Neanderthals and vocal tract don't have to agree.

IMO B.

The subject of the sentence should be Neanderthals as the non-underlined part of the sentence is plural & refers to them as having a shortcoming of no language. So, that leaves us with options A & B. D refers to the Neanderthal's vocal & so can be eliminated.

A - vocal tract is singular & is being compared to "those"of the apes.
B - Correct Subject-verb agreement.

What is being compared here (being is the rite usage ) ?

Vocal tracts of A and that of B

A. Compares a Vocal tract with those of apes (comparing many to one)

B. Compares a Vocal tract with an ape's

C . read very carefully here the non underlined portion ..
The vocal tracts ..were probably without language ..(no way )

D. The Neanderthal's vocal tracts did not resemble the apes' (btw do you know the difference b/w apes' and ape's..) also
The subject for the non underlined section

The Neanderthal's Vocal tracts... were probably without language ..(no way)

E. The comparison is rite ..
plural vocal tracts compares those of the apes .. but the non underlined portion needs a subject which is different
The vocal tracts of the Neanderthals... were probably without language(no way again)

Here there are two things which are tested .. the comparison and the sentence formation and most of us lose out the second one, trying to figure out the first one.

Most of the us (including me) would go for E,becos the comparison is rite..

I case you have any other explanation.. appreciate it..

Source : OG 10 , q.no 167

OA:B

in general grammar books there is word "distrubutive plural". this word consider correct to say that " the personS have the mounth or the mounthS", or that " the mounth of personS or the mounthS of personS"

that is why B is correct

So what is wrong with C and D?

CThe vocal tracts of Neanderthals resembled an ape's……. were probably without language.

Maybe the vocal tracts .....an ape's is wrong comprassion since tracts are plural and an ape's tract is singular right ?

D The Neanderthal's vocal tracts resembled the apes’

why no way
The vocal tracts of the Neanderthals... were probably without language(no way again)

Using the POE approach B appears to be right. C, D and E are incorrect, because they refer the vocal tracts to the rest of the sentence and this would mean that the vocal tracts are probably without language. Incorrect, subject is the Neanderthals.

A is refering a vocal tract(singular) to those, therefore it is incorrect.

Only B is acceptable, though it sounds a bit weird.

if C and D were correct, then the "Vocal tracts" were without language, not the apes. Vocal tracts are not the subject in this sentence. The apes are.
Hope that helps