Explanation: A VRM (Variable Range Marker) system is used in radar and similar display systems to project a visible marker on the screen, indicating a specific range or time delay from the transmitting source. In the digital control of such a system, a shift register is a fundamental component. It can be used to generate precise time delays or specific pulse patterns. By clocking data through the shift register, the system can determine the exact moment to trigger the display of the range marker, allowing its position to be accurately varied. A) A resolver is an electromechanical transducer used for measuring angular position, unrelated to range marking. B) An interference rejection circuit is a general component for reducing unwanted noise, not a core part of VRM generation. C) STC (Sensitivity Time Control) is used in radar receivers to adjust gain based on range, preventing receiver saturation from strong nearby echoes; it does not generate the marker itself.