Fact 1: Mammals conserve body heat with their hair or fur.

Fact 2: Dogs, of course, are mammals.

Given the two facts above, answer the question "How do dogs conserve body heat?" with the following options: 
- their blood cells
 - fur and fat
 - their nails
 - layers of fat
 - Exfoliation
 - sweating
 - their fur
 - their hair


 

       their fur  