7. Since the 1930’s aircraft manufacturers have tried to build airplanes with frictionless wings, shaped so smoothly and perfectly that the air passing over them would not become turbulent.
(A) wings, shaped so smoothly and perfectly
(B) wings, wings so smooth and so perfectly shaped
(C) wings that are shaped so smooth and perfect
(D) wings, shaped in such a smooth and perfect manner
(E) wings, wings having been shaped smoothly and perfectly so
这道题选B,为什么不选C呢，
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
这道题前人给出答案选A呀，这两道题有点相似呀，如果7题选B，这道题是不是应选E呀（管给的答案是E | 
