What is described as the center longitude of the Earth?

The Prime Meridian is the correct answer as it serves as the reference line for longitude at 0 degrees. It is the line that divides the Eastern and Western Hemispheres of the Earth and establishes the basis for the coordinate system used to define geographic locations. The Prime Meridian runs from the North Pole to the South Pole and passes through Greenwich, London, which is why it is often associated with Greenwich Mean Time (GMT).

In the context of global navigation and timekeeping, the Prime Meridian plays a crucial role because it allows for a standardized method of measuring longitude and helps in the coordination of time across different regions of the world.