Definition: 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").
Input: Fact1: friction is used for stopping a vehicle by brakes, Fact2: Friction is a Force that opposes motion., Question: A force that opposes motion is used for stopping vehicles by what? (A) wind (B) brakes (C) weight (D) spinning (E) shaking (F) trucks (G) fishtailing (H) rolling
Output:
B