On a documented small passenger vessel, what information must be permanently affixed in block-type letters and/or numerals to the main beam or other clearly visible interior structural part of the hull?

Correct Answer: Option A — The vessel's official number

46 CFR 67.121 requires that the official number assigned to a documented vessel be permanently affixed to the main beam or another primary structural part of the hull. This ensures the vessel's identity remains traceable even if the name or home port is altered.