You are presented with the question "Mammals can generate heat by" and the following answer choices: 
- hibernation
 - layers of fat
 - perspiration
 - aerobic exercise
 - respiration
 - exercise
 - with their fur
 - to stay warm

Now knowing that mammals generate heat mainly by keeping their metabolic rate high and aerobic exercise also contributes to the increased the metabolic rate, choose the best answer.


 

    aerobic exercise     