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, answer the question "What helps maintain body temperature?" with the following options: 
- hats
 - Lift
 - the inside of a refrigerator
 - fur
 - skin
 - arctic winds
 - freezing water
 - hair


 

    fur     