You are presented with the question "What keeps mammals warm?" and the following answer choices: 
- evaporation
 - Animal fur
 - staying warm
 - sweating
 - They have thick fur
 - with their fur
 - a layer of fat
 - Veins and arteries.

Now knowing that mammals have a layer of fat under the skin to help insulate the body and glass insulation keeps beverage warm for hours, choose the best answer.


 

       a layer of fat  