No person may serve as the person in charge of oil transfer operations on more than one vessel at a time __________.

Correct Answer: Option D — unless authorized by the Captain of the Port

33 CFR 155.710 prohibits a person from serving as the Person in Charge (PIC) of oil transfer operations on more than one vessel simultaneously. This regulation ensures undivided attention to critical safety and pollution prevention duties, with exceptions only granted by the Captain of the Port for specific operational needs.