Final answer:
Cortisol is a glucocorticoid hormone that is released in response to stress. It promotes the breakdown of stored nutrients to provide fuel for the body.
Step-by-step explanation:
Cortisol is a glucocorticoid hormone produced in the adrenal glands. It is released in response to stress and plays a role in regulating metabolism. It promotes the breakdown of stored nutrients, such as glycogen and triglycerides, to provide the body with fuel. Therefore, option d, 'It lowers when people are stressed,' is true about cortisol.