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

Fact 2: Fear also causes adrenaline to surge, which is part of the fight or flight response.

Given the two facts above, answer the question "threatening behavior causes" with the following options: 
- to move people
 - population movement
 - adrenaline to surge
 - hypothyroidism
 - a pathogens
 - Plant growth is reduced
 - Greenhouse gasses
 - hyperthyroidism


 

   adrenaline to surge      