What is the best source of information to find changes or additions to the routine communications frequencies of a Commercial Radio Station?

Correct Answer: Option A — ITU List of Coast Stations Part IV.

The ITU List of Coast Stations and Special Service Stations (List IV) is the authoritative international publication containing technical and operational details for coast stations, including frequency assignments, hours of operation, and services provided. It is the primary reference for GMDSS operators to verify current station information.