You are the Master of a 500-gross ton passenger vessel operating on rivers. Your vessel accidentally runs aground. Under the regulations for passenger vessels, you must notify the __________.

Correct Answer: Option B — nearest Coast Guard Marine Safety or Marine Inspection Office as soon as possible

46 CFR 4.05-1 requires the owner, agent, master, or person in charge to notify the nearest Coast Guard Marine Safety or Marine Inspection Office as soon as possible after a marine casualty, which includes grounding, regardless of the extent of damage or injury, to initiate necessary reporting procedures.