Option 2: cortisol -> The passage explicitly states that staying in an alert, active state (beta and gamma waves) "raises cortisol levels in the body, increasing feelings of stress and anxiety." This directly answers what levels are high in people on alert mode.
Hence, Option 2: cortisol -> The passage clearly mentions that the brain's default work state requires us to stay alert and active, but this raises cortisol levels in the body, which increases stress and anxiety -> correct