Detailed Instructions: 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").
Problem:Fact1: howling is used to warn other wolves by wolves, Fact2: Gray wolves are the largest members of the canine family., Question: What is used by canines to warn others? (A) antibodies (B) panting (C) noise (D) vibration (E) Chemicals (F) howling (G) lamphreys (H) hunting
Solution:
F