请教：白勇 Ch.6 #49

In recent years cattle breeders have increasingly used crossbreeding, In part that their steers should acquire certain charateristics and partly because crossbreeding is said to provide hybrid vigor.

D. partly because certain characteristics should be acquired by their steers

E. partly to acquire certain charateristics in their steers

答案事E，我选了D。白勇的解释是D里面的should使逻辑意思不合理。

可我觉得E在结构上很不对称啊，而且，原文里面有should，E把should拿掉了，一般也不会去选把

请大家指教，非常感谢

E. partly to acquire certain charateristics in their steers and partly because crossbreeding is said to provide hybrid vigor.

形式对称,

内容:前半句表目的,后半句表原因

E选项中的partly to acquire的逻辑主语应该是cattle breeders，难道是breeders acquire charicteristics吗？请指教

我也觉得这道题想不通。

我觉得，partly to后面接的是短语，partly because接的是句子，怎么平行呢？

partly because ...should , 如何翻译呢？

按照中国人的习惯就没有说，因为你应该怎样怎样的吧，这样的原因是说不过去的

Ｅ：ｐａｒｔｌｙ　（ｂｅｃａｕｓｅ　ｃｒｏｓｓｂｒｅｅｄｉｎｇ　ｉｓ）　ｔｏ　ａｃｑｕａｒｅ．．．ａｎｄ　ｐａｒｔｌｙ　ｂｅｃａｕｓｅ　ｃｒｏｓｓｂｒｅｅｄｉｎｇ　ｉｓ　ｓａｉｄ　ｔｏ　ｐｒｏｖｉｄｅ，省略相同的主谓。Ｅ用了平行的结构，而Ｄ的结构不与后面的ｐａｒｔｌｙ　ｂｅｃａｕｓｅ平行。

我觉得如果要省略的话，也应该省略后面那个啊，怎么会省略前面那个呢？

这一点我也不理解，请指教为什么E在结构上平衡而D反而不平衡，谢谢拉