The correct answer is C) ammonia inhalant. Ammonia inhalants are the proper stimulant for an unconscious person. This is because ammonia is a strong irritant that can help stimulate the respiratory system and revive an unconscious individual. Other options like coffee, tea, or whiskey and water are not appropriate as they would not provide the necessary stimulation to an unconscious person. Using an ammonia inhalant is the recommended first aid treatment for an unconscious or unresponsive individual, as it can quickly help restore consciousness without causing further harm.