明天考试了，请教一道语法题

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

a为什么没B好呢？

A 的"shaped so smoothly and perfectly " 不清楚修饰的是airplane 还是wings

B是同位语呀，GMAC比较PREFER同位语

同位语可以是"n,n","n,a/an +n","抽象名词+that""用一个概括性的名词去概括前面的解释，比如a program/ a practice that"，"n,n(该名词重复需要被修饰的名词）+that"或"n. the same n（该名词重复需要被修饰的名词）that"

多看看PREP就好啦~~~