Explanation: Amateur radio regulations permit brief on-air test transmissions as needed to ensure equipment is functioning correctly. This is a practical necessity for operators to check antenna match (SWR), power output, audio quality, and other parameters before engaging in communication. The key is that the transmission should be no longer than necessary to achieve its purpose and should cease during designated "silent periods" for emergency traffic. * **A) Between midnight and 6:00 AM local time:** This is incorrect. There is no specific time window mandated for testing; it can be performed whenever necessary. * **B) Only when authorized by the Commission:** This is incorrect. Routine testing of an amateur station, within the scope of the operator's license, does not require special, individual authorization from the FCC. * **D) After reducing transmitter power to 1 watt:** This is incorrect. While good operating practice suggests using the minimum power necessary, there is no specific regulatory requirement to reduce power to *exactly* 1 watt for all testing scenarios. An operator might need to test at various power levels to ensure proper operation.