The four satellites are needed to determine the location of an object using a GPS receiver.
Option: B
Explanation:
A GPS receiver specifically calculates the different speed of light (299,792 km / s) variations in the signals arriving from 4 or more satellites to determine the location of Longitude, Latitude and Highness.
There is requirement of four satellites, since each satellite data brings around the satellite in a sphere. You can limit the considerations down to a single point by programming the crossings. The collision of three satellites positions you on two possible points. The last satellite shows you exactly where you are.
