Answer:
Prime Meridian
Step-by-step explanation:
Prime meridian is a line of imagination that passes through Greenwich town in England separating the earth into two equal halves or hemispheres, namely the eastern and the western hemisphere. Along this line, the longitude is 0°. From this line, one can determine travelling in the eastern and the western direction.
It also helps in calculating the time zone at any place on earth.
Thus, the correct answer is Prime Meridian as it is used as the origin in a coordinate system.