Which two types of digital modulation are commonly used?

The correct answer identifies Phase Shift Keying (PSK) and Quadrature Amplitude Modulation (QAM) as commonly used types of digital modulation.

Phase Shift Keying is a method where the phase of a carrier signal is varied in accordance with the digital data signal. It allows for efficient transmission of data as it can represent multiple bits per symbol, particularly in its advanced forms like Differential PSK and Quadrature PSK.

Quadrature Amplitude Modulation combines both amplitude and phase variations to transmit data. It optimizes bandwidth efficiency by allowing multiple bits of data to be sent simultaneously, making it widely employed in modern communication systems, including broadband and digital television.

These modulation methods are favored because they are robust against noise and interference, making them ideal for various applications in digital communication systems. In addition, they match well with the requirements for bandwidth efficiency and the capacity demands of contemporary digital communication.

In contrast, other listed options feature modulation techniques that may be used but are less prevalent in modern digital communication systems, or they do not fit the digital modulation category as effectively as PSK and QAM do.