What does the Greenwich (Prime) Meridian represent?

The Greenwich (Prime) Meridian is significant as it serves as the baseline for measuring longitude, which is quantified in degrees east or west of this reference line. By establishing the Prime Meridian at 0 degrees longitude, it provides a standardized framework that enables navigation and geographic referencing across the globe. This facilitates various navigation-related tasks, from charting courses to determining time zones.

The other options misrepresent the concept of the Prime Meridian, as it specifically pertains to longitude rather than latitude or arbitrary designations of circles. The Prime Meridian is distinctly defined at 0 degrees E/W, while other longitudes (90 degrees E/W) reference different meridians. Similarly, latitude lines, like the equator, would not apply to a meridian that marks longitudinal references.