Explanation: For a chief radio officer on U.S. passenger ships, FCC regulations historically mandated a First Class Radiotelegraph Operator Certificate. This license signifies the highest level of proficiency in radiotelegraphy, including Morse code, advanced radio theory, and detailed knowledge of maritime radio regulations. This extensive qualification is crucial for managing all aspects of the ship's radio station, especially distress and safety communications, ensuring the safety of life at sea for a passenger vessel. A First or Second Class Radiotelegraph Operator Certificate with an endorsement (A) is not the minimum for the *chief* officer, who requires the First Class. A General Radiotelephone Operator License (C) covers radiotelephone operations but lacks the radiotelegraphy and advanced theory required for the chief's role, particularly concerning the specific requirements historically applied to these positions. A Marine Radio Operator Permit (D) is a basic license and entirely insufficient for such a critical, high-level maritime position.