The correct answer is A. Epinephrine
Step-by-step explanation:
Epinephrine or adrenaline is a hormone normally secreted by the adrenal glands which cause multiple effects such as pupil dilation, increase in the heartbeat, and changes in the muscles that are all par to the "fight or flight" response which is a natural response of animals when they perceive a dangerous situation and that made them either escape from the situation or face it. Indeed, the epinephrine is the main hormone involved in this reaction although other substances such as the cortisol, dopamine, and serotonin are also part of this. Therefore, the hormone that elicits the "fight or flight" response is the epinephrine.