Answer:
a. sympathetic nervous system
Explanation:
The sympathetic nervous system is part of the autonomic nervous system that is specifically responsible for the “fight or flight” response of the body when exposed to stress or threat. These responses to danger or stress are often involuntary. It is characterized with increased heart rate, constriction of blood vessels, profuse sweating, increased blood pressure etc.
When the sympathetic nervous system is activated in he presence of stress or a threat, epinephrine is released, initiating various reactions in the body against such threat or stimulus.