Correct Option: D

Radar is an object detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio waves or microwaves which bounce off any object in their path. In 1922 A. Hoyt Taylor and Leo C. Young, researchers working with the U.S. Navy invented Radar.