Answer:
The correct answer would be endocrinology.
The fight and flight response are stress response generated or regulated by hormones such as epinephrine and norepinephrine which are released from the adrenal gland.
Other hormones like testosterone, estrogen, and cortisol and neurotransmitters such as dopamine and serotonin also affect the organism's response to stress.
Thus, endocrinology would be the best career in order to learn more about these responses as endocrinology refers to the branch of science which deals with the endocrine system, hormones, and associated diseases.