What is the designation of the prime meridian that passes through Greenwich, England?

The prime meridian that passes through Greenwich, England is designated as 0°. This line serves as the starting point for measuring longitude and divides the Earth into the Eastern and Western Hemispheres. The significance of the prime meridian is profound in navigation, cartography, and timekeeping, as it is used as a reference for Coordinated Universal Time (UTC) and to coordinate global positioning systems.

The other options reference degrees of longitude that are either east or west of the prime meridian. For example, 90° indicates the meridian halfway around the world from Greenwich, while 180° marks the International Date Line, which is also an essential reference for time zones and navigation. The meridian at 45° is notably used in various contexts, such as defining the middle latitude in some regions, but is not a prime meridian itself. Thus, the designation of 0° is unique and fundamental to global navigation and mapping.