What device is used to remove fluid or vomit from an unconscious guest's mouth during care?

The correct choice is a suction device. This instrument is specifically designed to clear airways by removing fluids, such as vomit or saliva, from an unconscious person's mouth. Maintaining a clear airway is crucial in emergency situations, particularly for unconscious individuals who cannot manage their own secretions. The suction device creates a vacuum to effectively and safely remove blockages, preventing aspiration and allowing for safer ventilation.

Other devices listed are not suitable for this purpose. An Ambu bag is designed for providing positive pressure ventilation to a patient who isn't breathing, while a rescue mask is used for delivering rescue breaths or oxygen to a conscious or unconscious person. An oxygen tank is utilized for supplying supplemental oxygen, but it does not serve the function of clearing obstructions from the airway. Therefore, the suction device is the only appropriate option for this specific scenario.