tsalman

I think that 'shaped so smoothly and perfectly' modifies the 'wing'. The only thing that is missing is a subordinating conjunction. Since 'shaped so smoothly and perfectly..' is a noun clause, it should be linked with the rest of the sentence using a relative pronoun (that, which, whom, who etc.). (A) does not link modifier to the wing. i.e. no relative pronoun © uses a relative pronoun and by doing so, the modifier needs to be reconstructed. From 'shaped so smoothly..' to 'that are shaped so smooth and perfect'. I hope this helps.