Answer the following question: Fact 1: Mammals have a layer of fat under the skin to help insulate the body. Fact 2: Glass insulation keeps beverage warm for hours. Given the two facts above, answer the question "What keeps mammals warm?" with the following options: - evaporation - Animal fur - staying warm - sweating - They have thick fur - with their fur - a layer of fat - Veins and arteries.
Answer:
a layer of fat