The correct answer is D.
RADAR is an acronym for Radio Detection and Ranging. It is a system that uses radio waves to detect and locate objects. RADAR can be used to detect objects in the air, on the ground, and in the water. It is used by the military, police, and other organizations for a variety of purposes, including tracking aircraft, ships, and vehicles; detecting intruders; and weather forecasting.
Option A is incorrect because RADAR is not used to locate submerged submarines. Submarines are typically detected using sonar, which is a system that uses sound waves to detect objects.
Option B is incorrect because RADAR is not used to receive signals in a radio receiver. Radio receivers use antennas to receive radio waves.
Option C is incorrect because RADAR is not used to locate geostationary satellites. Geostationary satellites are typically located using optical telescopes.