I see nothing wrong with A. I know I have encountered this SC in the OG 10th
As I understand it, the way to solve this SC is as follows.
In recent years cattle breeders have increasingly used crossbreeding. Ask the question WHY?
And the answer becomes more obvious - that the steers should acquire certain characteristics. While C and E are tempting choices, because it seems to maintain llism. BEWARE!!
C is wrong, because it seems to be incomplete.
partly because of their steers acquiring certain characteristics/
C seems to suggest that the steers are acquiring characteristics from someone or something, but that someone or something isn't mentioned
E seems to suggest that the farmers are going "to acquire characteristics from their steers.
Thus C and E don't make sense. Given that. A is the best choice, and is grammatically correct, even though it isn't parallel.