Explanation: The First Class Radiotelegraph Operator Certificate, an FCC commercial license, requires a specific level of operational experience. One path to meet this requirement is demonstrating at least one year of aggregate experience in sending or receiving radiotelegraph messages. This ensures the operator possesses a comprehensive understanding and practical proficiency in Morse code operation necessary for a top-tier license. Option A is incorrect because six months of service as a radio operator on a U.S. ship is a requirement for a *Second Class* Radiotelegraph Operator Certificate, not the First Class. Option B is incorrect as merely holding a lower-class certificate for a period does not fulfill the *operational experience* requirement; actual time transmitting or receiving is necessary. Option D is incorrect as both A and B are incorrect.