Read the sentence below and answer the question that follows. Although Leonardo da Vinci's flying machines probably would not have flown, it cannot be argued that his ideas were not innovative and ingenious.

What is/are the problem(s) with this sentence, and what is the BEST way to revise the sentence to make it more effective? If it is best as it is written above, mark "correct as is."
A.
problems: passive voice and parallel structure
revision: Although Leonardo da Vinci's flying machines probably would not have flown, one cannot argue that his ideas were not innovating and ingenious.
B.
problems: passive voice and unclear expression
revision: Although Leonardo da Vinci's flying machines probably would not have flown, his ideas were both innovative and ingenious.
C.
problem: parallel structure
revision: Although Leonardo da Vinci's flying machines probably would not have flown, it cannot be argued that his ideas were not innovative and ingenious.
D.
correct as is