If mammals can also generate little bursts of heat by reacting to the cold, then mammals can also generate little bursts of heat by what?

Answer choices:
- the body's largest organ
 - reacting to the cold
 - flow of electrons
 - looking very cold
 - reacting to the news
 - considering being warm
 - Movement of an air mass
 - with their fur

 

  reacting to the cold        