请教一道语法题:GWD-13-6

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

答案选E..但是不是capability of doing...吗..我选A..

A，B我认为错在tested+that是宾语从句，that后面没主语错。B还错在OR后面的TO HELP不平行。

C是错早没主语+BE，还有OR HELPING不平行

D的HELPING 不平行