Sentence Correction

I came across the following sentence correction question on an official GMAT practice exam - Can anyone explain why choice C is correct? It looks like the difference is the word them versus which.

Question:

In Hungary, as in much of Eastern Europe, an overwhelming proportion of women work, many of which are in middle management and light industry.

A/ as in much of Eastern Europe, an overwhelming proportion of women work, many of which are in
B/ as with much of Eastern Europe, an overwhelming proportion of women works, many in
C/ as in much of Eastern Europe, an overwhelming proportion of women work, many of them in
D/ like much of Eastern Europe, an overwhelming proportion of women works, andy many are
E/ like much of Eastern Europe, an overwhelming proportion of women work, many are in

In Hungary, as in much of Eastern Europe, an overwhelming proportion of women work, many of which are in middle management and light industry.

A. as in much of Eastern Europe, an overwhelming proportion of women work, many of which are in
B. as with much of Eastern Europe, an overwhelming proportion of women works, many in
C. as in much of Eastern Europe, an overwhelming proportion of women work, many of them in
D. like much of Eastern Europe, an overwhelming proportion of women works, and many are
E. like much of Eastern Europe, an overwhelming proportion of women work, many are in

Quick approach:

A comparison must compare apples to apples: the right two things must be compared. In the SC above, what is happening in Hungary must be compared to what is happening in much of Eastern Europe. Eliminate B, D and E.

A: an overwhelming proportion of women work, many of which
Here, which seems to refer refer to women.
On the GMAT, which cannot serve to refer to people.
Also, a which-clause must be preceded by a NOUN.
Here, many of which are (a which-clause) is preceded by a VERB (work).
Eliminate A.

The correct answer is C.

In the OA, many of them in middle management is an ABSOLUTE PHRASE modifying the entire preceding clause.
An absolute phrase:

-- typically is composed of a noun + noun modifier, perhaps with a few other words
-- often includes a participle
-- does NOT include a main verb
-- does not include a conjunction (such as and)
-- is connected to the rest of the sentence by a comma or dashes
-- supplies context for the preceding clause

TWO KEY DIFFERENCES between COMMA + which-clause and COMMA + absolute phrase:
COMMA + which-clause REQUIRES A VERB and MUST BE PRECEDED BY A NOUN.
COMMA + absolute phrase does NOT include a verb and does NOT have to be preceded by a noun.

Thank you both for the help.