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: an animal usually requires a warm body temperature for survival, Fact2: Mammals are also warm-blooded and are covered with hair or fur., Question: What helps maintain body temperature? (A) hats (B) Lift (C) the inside of a refrigerator (D) fur (E) skin (F) arctic winds (G) freezing water (H) hair
A:
D