一道关于对称的旷世难题...

396. 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）
(E) partly to acquire certain characteristics in their steers

这题看了答案以后也想不通,根据句子对称partly没有问题,但是应该是partly because前后对称把....而且即使看答案能想通,有没有高手XDJM能告诉我真正能避免选D 的方法.....感谢!

感谢...