GMAT Sentence Correction (SC) | Re: Like ants, termites have an elaborate social structure in

Like ants, termites have an elaborate social structure in which a few individuals reproduce and the restare serving the colony by tending juveniles, gathering food, building the nest, or they battle intruders.

A. are serving the colony by tending juveniles, gathering food, building the nest, or they battle
B. are serving the colony in that they tend juveniles, gather food, build the nest, or battle
C. serve the colony, tending juveniles, gathering food, building the nest, or by battling
D. serve