The correct answer is B) each manned watch station. The United States Coast Guard regulations require that, in addition to the life jackets stowed in readily accessible places, life jackets must also be stowed at each manned watch station on a vessel. This ensures that crew members on watch have immediate access to life jackets in the event of an emergency. The other options are incorrect because they do not align with the specific Coast Guard regulation. Life jackets are not required to be stowed at fire stations (A), the mess room (C), or each lifeboat (D), as the primary requirement is to have them readily accessible and at manned watch stations.