You are presented with the question "How can mammals generate heat?" and the following answer choices: 
- layers of fat
 - Ice cubes
 - wishing
 - Depleting energy stores
 - death
 - with their fur
 - raising their temperature
 - by keeping them warm

Now knowing that mammals can also generate little bursts of heat by shivering and shivering costs the bird, however, by depleting energy stores, choose the best answer.


 

    Depleting energy stores     