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. (A) in part that their steers should acquire certain characteristics (B) in part for the acquisition of certain characteristics in their steers (C) partly because of their steers acquiring certain characteristics (D) partly because certain characteristics should be acquired by their steers (E) partly to acquire certain characteristics in their steers 看到划线后的and就想到平行，然后就错选了D，答案是E，不理解为什么，请老师讲解一下。谢谢！