The correct answer is B. PSK.
PSK stands for Phase-Shift Keying. It is a modulation technique in which the phase of a carrier wave is varied in accordance with the digital data to be transmitted. PSK is a very efficient modulation technique, and it is widely used in digital communications.
There are several different types of PSK, including binary PSK (BPSK), quadrature PSK (QPSK), and eight-phase PSK (8PSK). BPSK is the simplest type of PSK, and it uses two phases to represent the two binary digits, 0 and 1. QPSK uses four phases, and 8PSK uses eight phases.
PSK is a very reliable modulation technique, and it is often used in applications where high data rates are required. However, PSK is not as robust as some other modulation techniques, such as Frequency-Shift Keying (FSK). This is because PSK is more susceptible to noise and interference.
PIA stands for Pulse-Interval Amplitude Modulation. It is a modulation technique in which the amplitude of a pulse is varied in accordance with the digital data to be transmitted. PIA is not as widely used as PSK, but it is still used in some applications.
PM stands for Phase Modulation. It is a modulation technique in which the phase of a carrier wave is varied in accordance with the digital data to be transmitted. PM is similar to PSK, but it is not as efficient. This is because PM requires a higher bandwidth than PSK.
D is incorrect because it is not a modulation technique.