In recent years cattle breeders have increasingly used crossbreeding, in part that their steers should acquire certain characteristics and partly because crossbreeding is said to provide hybrid vigor.
(D) partly beacuse certain characteristics should be acquired by their steers
(E) partly to acquire certain characteristics in their steers
这题我第一眼想选D,但第二眼发现certain characteristics should be acquired by their steers说不通,尤其是这个awkward的被动结构里,steers并非characteristics的施动者。而E项不定式是GMAC比较喜欢的,虽然部分影响了平行,但简洁明了