Final answer:
Diuretics increase a person's risk of heat-related emergencies.
Step-by-step explanation:
The medication that increases a person's risk of a heat-related emergency is C. Diuretics. Diuretics are drugs that increase urine output and can lead to dehydration, which can increase the risk of heat-related emergencies. They are commonly used to treat hypertension and fluid retention. Examples of diuretics include hydrochlorothiazide and furosemide.