Fact 1: Mammals have a layer of fat under the skin to help insulate the body.

Fact 2: Insulation is very important in a cold climate like Arkhangelsk.

Given the two facts above, answer the question "What aspect of mammals is especially important in cold climates?" with the following options: 
- layer of body fat under skin
 - lips
 - sweat glands
 - To conserve energy
 - toes
 - food and shelter
 - It helps them survive
 - by keeping them warm


 

 layer of body fat under skin        