Correct option is A
A wave trap is a device used in power line carrier communication (PLCC) systems.
It is essentially a resonant circuit (LC circuit) designed to block high-frequency communication signals (30–500 kHz) from entering certain parts of the power system (like generators or substations), while allowing 50/60 Hz power frequency to pass.
It resonates at the carrier frequency and presents a high impedance, effectively "trapping" the high-frequency wave and preventing its propagation beyond a point.
