The correct option is
A Hormone of the adrenal gland
Epinephrine is also known as adrenaline secreted by the adrenal gland. It is a fight or flight hormone that acts upon the vascular system-dilates the arteries , increases heart rate, dilates the pupil, increases blood sugar level etc to help a person to tackle a threatening situation.
So, the correct answer is 'Hormone of the adrenal gland'