You are presented with the question "threatening behavior causes the what and hormones to flood the body" and the following answer choices: 
- heart to race
 - relaxation
 - calmness
 - deep thought
 - nervous system
 - circulatory system
 - hypothyroidism
 - cells of organisms

Now knowing that threatening behavior causes a fight-or-flight response in animals and hairs stand on end, the heart races and fight or flight hormones flood the body, choose the best answer.


 

 heart to race        