A and E: shaped SMOOTHLY
smoothly means performed WITHOUT DIFFICULTY.
Thus, shaped smoothly means shaped WITHOUT DIFFICULTY, implying that the process of shaping the wings is easy.
Not the intended meaning.
The intended meaning is not that the shaping PROCESS is smooth but that the WINGS themselves are SMOOTH.
Eliminate A and E.

C: are shaped so smooth and perfect
Here, smooth and perfect (two adjectives) seem to modify are shaped (a verb).
An adjective cannot modify a verb.
An adjective must serve to modify a NOUN.
Eliminate C.

D: shaped in such a smooth and perfect manner
Like A and E, this option implies that the MANNER of shaping the wings is EASY.
Not the intended meaning.
The intended meaning is not that the shaping MANNER is smooth but that the WINGS themselves are SMOOTH.
Eliminate D.
OA: Since the 1930's aircraft manufacturers have tried to build airplanes with frictionless wings, wings so smooth and so perfectly shaped that the air passing over them would not become turbulent.

The portion in green is an example of a RESUMPTIVE MODIFIER.
A resumptive modifier:
-- repeats a key word in the sentence
-- conveys additional information about that key word
-- often includes a that-clause
-- usually appears at the end of a sentence
In the OA, the resumptive modifier makes it clear that so smooth and so perfectly shaped refers only to the WINGS, not to the entire airplane.