What is used to prevent contamination of a potable water system supplying a plumbing fixture such as a galley sink from a backup of sewage sanitary drains?

Correct Answer: Option D — Location of the potable water spigots above the rim of the galley sink.

To prevent back-siphonage or cross-contamination, 46 CFR requires an air gap between the potable water outlet and the flood rim of the fixture. Locating the spigot above the sink's rim ensures that if the drain backs up, the contaminated water cannot physically reach the potable water supply line.