Q: You are presented with the quiz "Propellers are on some airplanes primarily to give" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "producing thrust causes something to move" and "airplanes create thrust using propellers, jet engines , or rockets ". So, what's the best answer to the question?

pick from the following.
(i) stability.
(ii) protection from bird strikes.
(iii) speed.
(iv) motion.
(v) engine cooling.
(vi) energy.
(vii) noise cancellation.
(viii) power.
A:
(iv)