You are presented with the quiz "Mammals can also generate little bursts of heat by what?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "mammals can also generate little bursts of heat by shivering" and "an inability to shiver or react to the cold can contribute to hypothermia". 

So, what's the best answer to the question?


 

  reacting to the cold         