Explanation: A display power supply provides the specific DC voltages necessary for the internal electronics of the display unit. 5 volts DC is the standard operating voltage for most digital logic circuits, which control the display's functions, character generation, and pixel addressing. $\pm$12 volts DC are common bipolar supply voltages used for analog circuits like operational amplifiers. These are essential for signal conditioning, video processing, and particularly for sweep circuits found in older Cathode Ray Tube (CRT) displays or precision analog driving circuits in modern display technologies that require accurate voltage control over a range. Option A is incorrect because pulse forming networks (PFNs) are typically associated with high-power pulsed transmitters (like radar), requiring kilovolts, not 18V, and are not part of a display's internal power supply. Option C is incorrect because antenna resolver circuits are part of the antenna positioning system, not the display's internal power supply, and use different AC excitation voltages.