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").
Q: Fact1: some animals' fur grows thicker for staying warm in the winter, Fact2: Mammals have hair and fur., Question: Why do some animals have hair that grows longer during the winter? (A) It expands (B) to make braids (C) to wear a scarf (D) to attract mates (E) When it's cold (F) to stay warm (G) It remains dormant (H) genetic diversity
A:
F