The reams of studies and drafts documented by Gustave Eiffel indicate that the design of the Eiffel Tower generally
emerged not in a rapid manner but developed painstakingly from multiple trial prototypes.
(A) emerged not in a rapid manner but developed painstakingly
(B) emerged not in a rapid manner but was painstakingly developed
(C) did not emerge in a rapid manner but developed painstakingly
(D) did not emerge in a rapid manner but had painstakingly developed
(E) did not emerge in a rapid manner but it was painstakingly developed
Don't read my issue with the official answer before solving the problem.
Is the official answer's meaning correct?
I feel that the OA implies that "the design" does 2 things:
1- The design did not emerge... (which seems fine to me)
2- The design developed ...
I feel that the OA says "the design" actually developed something instead of being developed. Shouldn't "developed" be in passive voice ( was developed)?
The OA mentions that one reason B is wrong is that the passive voice is inappropriate:
"Answer choice B makes a similar error in parallel structure to that of the original sentence; further, the passive voice 'were developed' is inappropriate."
By the way the OA says ' were developed' instead of 'was developed' when it quotes choice B.