Answer:
a. epinephrine.
Explanation:
Discovered in 1895, epinephrine, the hormone of "fight or flight" is a key neurotransmitter as man evolved.
Produced by the adrenal glands, it s main function is to trigger a quick response to potenital threats, seen an increased blood pressure to muscles, heart rate, pupils dilatation and increased metabolyizing of suger.
The incorrect levels of epinephrine will characterize a person suffering an anxiety disorder. If a situation requieres a stress response, epinephrine will help a living organism like mammals to answer quickly and surive.