Final answer:
The correct answer to the characteristics of the exhaustion phase in Selye's GAS is 'a) Decreased resistance to disease and infection', indicating a depletion of bodily resources and potential for serious health issues.
Step-by-step explanation:
The exhaustion phase of the general adaptation syndrome (GAS) is characterized by decreased resistance to disease and infection. This stage follows the initial alarm reaction, where the fight-or-flight response is activated, and the stage of resistance, where the body adapts to the stressor if it continues. In the exhaustion phase, prolonged stress leads to a depletion of the body's physical resources, contributing to various health problems such as depression, a suppressed immune response, severe fatigue, and potentially fatal health events like heart attacks. Therefore, the correct answer is (a) Decreased resistance to disease and infection.