What is the key function of radar systems in terms of object detection?

Correct option is B

​$$\text{Radar (Radio Detection and Ranging) works by:} \\[8pt]\bullet \ \text{Transmitting electromagnetic (radio) waves toward a target} \\[4pt]\bullet \ \text{Receiving the reflected (echo) signals from objects} \\[8pt]\text{Analyzing the time delay, frequency shift, and amplitude of the echoes to determine:} \\[6pt]\bullet \ \text{Distance (range)} \\[4pt]\bullet \ \text{Velocity (via Doppler shift)} \\[4pt]\bullet \ \text{Direction and sometimes size of the object}$$​​