Mammals can also generate little bursts of heat by shivering, and shivering causes muscle contractions to warm the body. Given these facts, mammals can also generate little bursts of heat through what among the following options:
- Movement of an air mass
 - crackling
 - Veins and arteries.
 - electromagnetic energy
 - house
 - fire
 - muscle contractions
 - aerobic capacity


 

       muscle contractions  