The correct option is D Wings
Option C: It's mentioned in the passage, "To fly, it is not necessary to have wings; there are machines."
It is not necessary to possess WINGS. Hence, C is correct.
Option A: 'Feet' is not mentioned in relation to flying.
Option B: Similarly, 'arms' are also not mentioned with respect to flying.
Option D: 'Machines' is not correct, because if one is flying with the help of machines, then they are very much necessary.
Hence A, B and D are incorrect.