https://www.beatthegmat.com/many-of-them ... 79-15.html

the question is already discussed in abve link

kindly check before posting

however

i will go with B

controversial one, but I would go for C with this one. Here's why

patchwork is the subject of the sentence here, and the author tries to put forward that the patchwork bustles with farmers, now the patchwork can not surround the San Joaquin Valley. Actually green fields surround the valley and we are talking about the patch work in the green fields.

So I think surround is better. "Them" is not correctly referring to the farmers. And once encountered with the subjective and nominative case, I would choose many of who because in the latter part of the sentence the farmers are used as a subject.

Please correct me if I am wrong

being patchwork the subject of this sentence the verb should be singular
I'll go with B too
which is OA?

OA is not clear but seems to be B based on experts' reasoning in the previous post, indicated by Phoenix above.

gmatnmein2010 wrote:In good years, the patchwork of green fields that surround the San Joaquin Valley town bustles with farm workers, many of them in the area just for the season.

(A) surround the San Joaquin Valley town bustles with farm workers, many of them
(B) surrounds the San Joaquin Valley town bustles with farm workers, many of whom are
(C) surround the San Joaquin Valley town bustles with farm workers, many of who are
(D) surround the San Joaquin Valley town bustle with farm workers, many of which
(E) surrounds the San Joaquin Valley town bustles with farm workers, many are

GMATNMEIN2010

It has been informed you earlier as well, to SEARCH before you post
Besides, mention the source of your questions

I am afraid that any new such post by you that would be without SOURCE will have to be deleted otherwise