Final answer:
Open the patient's airway using a head-tilt, chin-lift maneuver is the immediate action to be taken to clearing the airway which is most critical when a person has slow, wet sounding respirations and has vomited.
Step-by-step explanation:
In the situation described, where a 19-year-old female college student has been drinking alcohol and is found unconscious with slow, wet-sounding respirations and evidence of vomiting, the immediate concern is to ensure that her airway is clear to prevent asphyxiation. Therefore, the correct next step would be option D, to open the patient's airway using a head-tilt, chin-lift maneuver. This procedure is critical to prevent the blocking of the airway by the tongue or any vomit that may be present.
After the airway has been secured, other steps such as checking for pulses and determining the respiratory rate can follow, but the airway must be the first priority to ensure oxygen can reach the lungs. If after opening the airway the breathing does not improve significantly, or if it remains labored or obstructed, assist respirations with a bag-valve-mask device should be considered and performed by a person trained in its use. Initiating CPR might be necessary if the patient is found pulseless.