Explanation: A RADAR system operates by sending out short pulses of radio energy and then listening for the reflections (echoes). The indicator display, such as a Plan Position Indicator (PPI) or A-scope, visually represents these echoes, correlating the time elapsed since the pulse was sent to the distance of the reflecting object. For the indicator to accurately display the returns from each individual transmitted pulse, its sweep mechanism must initiate a new sweep cycle every time a pulse is sent out. This means the rate at which the display's sweep begins and resets, which is its sweep frequency, must be precisely synchronized with the rate at which the radar transmits pulses. This fundamental rate is the **Pulse Repetition Frequency (PRF)**. If the radar transmits 1000 pulses per second (PRF = 1 kHz), the display must sweep 1000 times per second to present the information from each pulse. * **A) Carrier frequency** is the frequency of the radio waves within each pulse and affects range, resolution, and propagation, but not the pulse rate. * **B) Pulse width** is the duration of a single transmitted pulse and influences minimum range and range resolution. * **C) Duty cycle** is the ratio of the pulse width to the pulse repetition interval (1/PRF) and is a measure of transmitter "on time," not the rate of new pulse transmissions.