Answer the following question: Fact 1: An animal usually requires a warm body temperature for survival. Fact 2: Mammals are also warm-blooded and are covered with hair or fur. Given the two facts above, what helps maintain body temperature?

Select from: 1). hats 2). Lift 3). the inside of a refrigerator 4). fur 5). skin 6). arctic winds 7). freezing water 8). hair
Answer:
4).