Which type of modulation is used for FM (Frequency Modulation)?

The correct choice highlights that FM (Frequency Modulation) is characterized by frequency deviation relative to a carrier wave. In FM, the information signal modifies the frequency of the carrier wave, resulting in variations in frequency rather than amplitude. This means that as the amplitude of the input signal increases or decreases, the frequency of the output signal shifts accordingly, deviating from the center frequency of the carrier.

This modulation technique is particularly effective in reducing the impact of noise and interference, making FM widely used for high-fidelity broadcasts, such as FM radio. The distinction between frequency deviation and amplitude variation is crucial in understanding how FM operates, as variations in amplitude are not part of the modulation process for FM; instead, it exclusively relies on changes in frequency to convey information.

Other modulation types mentioned in the options, such as pulse modulation and digital modulation, do not represent frequency modulation and have different methodologies and applications. Pulse modulation encodes information in pulses, while digital modulation involves encoding data onto a carrier in a digital form, neither of which align with the principles of frequency modulation.