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

Choice E is best; it best indicates purpose for crossbreeding—partly to acquire. In A, in part that does not grammatically connect the underlined portion to the first part of the sentence (the independent clause). In both A and B, in part is not parallel with and partly in the non-underlined portion. Choice C causes a misreading, suggesting that the steers’ acquisition has caused the crossbreeding. D awkwardly and illogically shifts to the passive voice: certain characteristics should be acquired by their steers;) the steers, however, are not agents in the acquisition.

我想问问划红线部分，为什么?

前面的讨论我翻过没有，多些大家。

thanks a lot !!!