Answer: A.it is a relatively new human adaptation.
Step-by-step explanation:
Fight or flight response is a response shown by a human or animal body towards acute stress. It is a physiological reaction that occurs in response to the perceived attack, survival threat and attack. The animals or humans react to threats by the hormonal secretion from sympathetic nervous system. This prepared animals for fighting. The hormonal secretions like catecholamines, epinephrine and nonepinephrine helps in generation of response. Neurotransmitters dopamine, estrogen, testosteron e and cortisol affects how organisms react to the stress.
Fight-or-flight reaction is not a relatively new human adaptation but it is evolved as a survival mechanism which was also present in primitive human beings and mammals and helped them to react in the life-threatening situations.