Explanation: RADAR systems transmit short, powerful bursts of radio frequency energy at a fixed and regular rate, known as the Pulse Repetition Frequency (PRF). When a communications receiver intercepts these strong, repetitive pulses, its detector and audio amplifier stages process this structured signal. If the RADAR's PRF falls within the audible range of the receiver's audio passband (typically 300-3000 Hz), the receiver will demodulate these rapid, consistent pulses as a distinct audio frequency. Since the RADAR's PRF is constant for a particular system, the resulting audio output is a continuous, unchanging "steady tone." A varying tone (A) would imply a changing PRF. Static (B) and a hissing tone (C) are characteristics of random or broadband noise, not a highly structured, repetitive pulsed signal.