In this task, you are given two facts, and a multiple-choice question. Based on the given facts, answer the question with index of the correct option (e.g, "A").
Q: Fact1: producing thrust causes something to move, Fact2: Airplanes create thrust using propellers, jet engines , or rockets ., Question: Propellers are on some airplanes primarily to give (A) stability (B) protection from bird strikes (C) speed (D) motion (E) engine cooling (F) energy (G) noise cancellation (H) power
A:
D