Explanation: An artificial antenna used for testing a transmitter is commonly known as a **dummy antenna** (A) or a **dummy load** (B). Both terms refer to a non-radiating device that simulates the electrical characteristics of an actual antenna, presenting a proper impedance (typically 50 ohms) to the transmitter. The primary purpose of using such a device is to **prevent undesired radiation** (C) during testing and tuning. Instead of transmitting radio frequency (RF) energy into the air, the dummy load converts it into heat. This ensures that operators comply with FCC regulations by not transmitting off-frequency, with excessive power, or causing interference while performing maintenance or adjustments. Since options A, B, and C are all accurate descriptions or functions of this essential testing tool, "All of the above" is the correct choice.