After pinching a victim's nostrils, how can a rescuer best provide an airtight seal during mouth-to-mouth ventilation?

Correct Answer: Option D — by applying his mouth tightly over the victim's mouth

Effective mouth-to-mouth ventilation requires a positive pressure seal to ensure air enters the lungs rather than escaping. By placing your mouth tightly over the victim's mouth and maintaining a patent airway via head-tilt/chin-lift, you maximize tidal volume delivery while preventing gastric distension and ensuring adequate oxygenation.