Fossils of thumb-length primates that they had recovered from the fissure-filled sediments of a limestone quarry in China in 1996, easily represents the smallest known primates, with one species estimated to have weighed only 10 grams.

A. primates, that they had recovered from the fissure-filled sediments of a limestone quarry in China in 1996, easily represents the smallest known primates -- There is an SV error. The comma before that is also ungrammatical.

B. primates that were recovered from the fissure-filled sediments of a limestone quarry in China in 1996, are the smallest known primates ---This means to say that the fossils themselves are the primates. No. The fossils represent the primates. In addition, C is crisper.

C. primates, recovered from the fissure-filled sediments of a limestone quarry in China in 1996, easily represent the smallest known primates – seems to be the best choice.

D. primates which were recovered from the fissure-filled sediments of a limestone quarry in China in 1996, easily represent the smallest known primates – There is no comma before which. This is a major error in at least GMAT. In addition, why is the comma after1996?

E. primates, recovered from the fissure-filled sediments of a limestone quarry in China in 1996, easily representing the smallest known primates --- This choice is a fragment.
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Not able to understand what is wrong in D

In what cases, which cannot be used? What's wrong with option D?

Fossils of thumb-length primates that they had recovered from the fissure-filled sediments of a limestone quarry in China in 1996, easily represents the smallest known primates, with one species estimated to have weighed only 10 grams.

A. primates, that they had recovered from the fissure-filled sediments of a limestone quarry in China in 1996, easily represents the smallest known primates- no need of past perfect as there is no sequence

B. primates that were recovered from the fissure-filled sediments of a limestone quarry in China in 1996, are the smallest known primates- Meaning error: they represent smallest primates

C. primates, recovered from the fissure-filled sediments of a limestone quarry in China in 1996, easily represent the smallest known primates

D. primates which were recovered from the fissure-filled sediments of a limestone quarry in China in 1996, easily represent the smallest known primates- No comma before which

E. primates, recovered from the fissure-filled sediments of a limestone quarry in China in 1996, easily representing the smallest known primates- Fragment

The problem with D is "... primates which were recovered from the fissure-filled sediments of a limestone quarry ..."

This long phrase suggests that the PRIMATES were recovered from the quarry, when of course it was the FOSSILS that were discovered

"WHICH" almost always refers to the noun that is just before it, and you can expect to see a comma before the "WHICH"

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A. primates, that they had recovered from the fissure-filled sediments of a limestone quarry in China in 1996, easily represents the smallest known primates - 'Fossils' is the plural subject and verb 'represents' is not in agreement with the subject.

B. primates that were recovered from the fissure-filled sediments of a limestone quarry in China in 1996, are the smallest known primates - Fossils themselves are the primates? Does not make any sense.

C. primates, recovered from the fissure-filled sediments of a limestone quarry in China in 1996, easily represent the smallest known primates - Correct Choice.

D. primates which were recovered from the fissure-filled sediments of a limestone quarry in China in 1996, easily represent the smallest known primates - Which modifies the immediate preceding Noun which is Primates in this case. Recovery of primates does not make any sense.

E. primates, recovered from the fissure-filled sediments of a limestone quarry in China in 1996, easily representing the smallest known primates - Main verb is absent in the sentence. its fragment.
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