Correct option is D
Pulse-width modulation: PWM is widely used in power modulators because it allows for precise control of power output by varying the width of pulses in a square wave signal.
Amplitude modulation (AM): AM changes the amplitude of a carrier wave, not its width, which is not how power is controlled in most modulators.
Delta modulation (DM): DM is primarily used for signal quantization, not power control.
Frequency modulation (FM): FM changes the frequency of a carrier wave, which is not the typical method for adjusting power output in power modulators.
