Explanation: Tuning a transmitter involves adjusting its resonant circuits, particularly the final amplifier stage and antenna matching unit, to achieve maximum power transfer to the antenna and ensure an efficient operation. When these circuits are mistuned, they present an improper load to the amplifier. This causes a significant portion of the amplifier's input power to be dissipated as heat within its components (like transistors or vacuum tubes) instead of being radiated as RF. Running the transmitter at full power during this mistuned state can quickly overheat and destroy expensive final amplifier components. By tuning at reduced power, the amount of dissipated heat during the adjustment process is minimized, effectively protecting the components from damage while optimal tuning is achieved. Option B is incorrect because tuning at normal or full power significantly increases the risk of component damage due to excessive heat generation in a mistuned state. Option C is incorrect; plate tank circuits (in tube amplifiers) are tuned for *minimum* plate current (indicating maximum efficiency and output power for a given drive) rather than maximum DC current. Maximum plate current typically signifies a mismatch and high power dissipation, which can lead to damage.