According to selye, some people may develop illnesses such as high blood pressure or a weakened immune system during the stage of the general adaptation syndrome. alarm collapse exhaustion resistance

I believe the answer for the above question is exhaustion stage.
Hans selye, described three predictable stages the body uses to respond to stressors, called general adaptation syndrome (GAS). The first stage is alarm stage, which provides burst energy, then the resistance stage where the body attempts to resist or adapt to the stressor, and finally the exhaustion stage. During the resistance stage, the body uses its resources of flight off the stressor. It is not until the next stage, exhaustion, that bodily resources are so depleted that stress-related diseases can develop.