The rescuer can best provide an airtight seal during mouth-to-mouth resuscitation by pinching the victim's nostrils and __________.

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

Under USCG Deck Safety, SOLAS Chapter III, and 46 CFR regulations, when addressing 'The rescuer can best provide an airtight seal during mouth-to-mouth resuscitation by pinching the victim's nostrils and', the mandated standard is: 'applying his mouth tightly over the victim's mouth'.