The purple arrow on the map above is pointing to the an important line of latitude.

The correct answer is:

The Equator.

The Equator is the great circle around the Earth that is everywhere equidistant from the geographic poles. It lies in a plane perpendicular to the Earth’s axis. This geographic line separates the Earth into the Northern and Southern hemispheres and creates the theoretical reference line from which latitude is calculated. The Equator is the line with 0° latitude

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