大全上另一道题，runon问题请教----

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（A）

(E) surrounds the
San Joaquin Valley town bustles with farm workers, many are

答案是A，后面的many of them in the area just for the season.是同位语说明成分？？

另外C为什么不对呢？请教大家