Under the federal regulations of 33CFR Subchapter O, if a vessel equipped with a Type III Marine Sanitation Device enters a body of water where the discharge of untreated sewage is prohibited, which of the following methods of securing the device to prevent the discharge of sewage is UNACCEPTABLE?

Correct Answer: Option C — Closing and tagging each valve leading to an overboard discharge.

33 CFR 159.7 requires that overboard discharge valves for Type III MSDs be secured to prevent accidental discharge. Acceptable methods include padlocking, using non-releasable wire ties, or removing the valve handle. Simply tagging a valve is insufficient, as it does not physically prevent the valve from being opened by unauthorized personnel.