一道语法题

yaoxiayi

After more than four decades of research and development, a new type of jet engine is being tested that could eventually propel aircraft anywhere in the world within two hours or help boost cargoes into space at significantly lower costs than current methods permit.

A.    tested that could eventually propel aircraft anywhere in the world within two hours or help
B.    tested that could eventually have the capability of propelling aircraft anywhere in the world within two hours or to help
C.    tested, eventually able to propel aircraft anywhere in the world within two hours, or helping
D.    tested, and it eventually could propel aircraft anywhere in the world within two hours or helping
E.    tested, and it could eventually have the capability to propel aircraft anywhere in the world within two hours or help

答案是A/E,我觉得应该是C
首先A中的that到底是什么成分呢？
E中的capability不简洁
虽然Ｃ也不是很好，但是相比之下，我觉得Ｃ最好

Souref

答案是A还是E？
A的从句有问题；
C也不能选，parallelism是严格规则；
似乎只能选E了
capability还好了，不算特别不简洁，另外需要注意简洁不是硬纪律