Final answer:
The scenario where Nancy encounters a rattlesnake and feels a burst of energy to run represents the d. alarm reaction stage of the general adaptation syndrome.
Step-by-step explanation:
Nancy is hiking in the mountains when she comes across a rattlesnake looking right at her and feels a burst of energy to run away from the danger. This scenario illustrates the d. alarm reaction stage of the general adaptation syndrome (GAS). The alarm reaction is the body's immediate response to a stressor, presenting with a cascade of physiological reactions that provide energy to manage the situation. It is part of the fight-or-flight response, which is triggered by the release of hormones like epinephrine and norepinephrine that prepare the body for extreme physical exertion. This stage is the first phase of GAS, which is then followed by the stages of resistance and, if stress continues for a prolonged period, exhaustion.