Explanation: When the antenna circuit, along with its matching network, is brought into resonance, it means the system is being tuned to present an optimal load to the final amplifier. The purpose of this tuning is to ensure efficient transfer of radio frequency (RF) power from the amplifier to the antenna. For most RF power amplifiers (especially Class C or AB amplifiers common in amateur radio), when the output circuit is properly matched and resonated to the antenna, the amplifier is able to deliver maximum power into that load. As the amplifier delivers more power, it draws a greater average current from its plate (or collector/drain) power supply. Therefore, as the antenna circuit is brought into resonance for efficient power transfer, the plate current of the final amplifier will typically increase. * **A) It will increase:** This is correct because the amplifier is now working more efficiently into a matched load, delivering more power, which requires a higher average plate current. * **B) It will decrease:** While an *unloaded* plate tank circuit might show a current dip at its own resonance, when *loading* the amplifier for power transfer to an antenna, the average plate current increases as the load becomes optimal. * **C) It will remain constant:** Tuning an output circuit significantly changes the load seen by the amplifier, thus affecting its current draw. * **D) None of the above:** Since A is the accurate observation, this option is incorrect.