Final answer:
Stan is in the a)alarm reaction phase of the General Adaptation Syndrome, characterized by the fight-or-flight response, during which his body prepares for immediate action in response to the stress of being rear-ended.
Step-by-step explanation:
Stan is currently in the alarm reaction phase of the General Adaptation Syndrome (GAS). This phase is characterized by the fight-or-flight response, a physiological reaction to a perceived threat or stress. As Stan gets out of his car after being rear-ended, his sympathetic nervous system is activated, and his body is primed for action, which is consistent with the symptoms of the alarm phase. This is when the body alerts the individual with a cascade of physiological reactions, like increased heart rate and elevated adrenaline levels, to manage the stressful situation.