Fact 1: Threatening behavior causes a fight-or-flight response in animals.

Fact 2: Hairs stand on end, the heart races and fight or flight hormones flood the body.

Given the two facts above, answer the question "threatening behavior causes the what and hormones to flood the body" with the following options: 
- heart to race
 - relaxation
 - calmness
 - deep thought
 - nervous system
 - circulatory system
 - hypothyroidism
 - cells of organisms


 

 heart to race        