Question

which line represents 0° longitude?
the prime meridian
the equator
the international date line
the tropic of capricorn

Explanation:

Longitude lines are imaginary vertical lines measuring east-west positions. The prime meridian is defined as 0° longitude, serving as the reference for all other longitude values. The equator is 0° latitude (north-south reference), the international date line is ~180° longitude, and the Tropic of Capricorn is a latitude line (~23.5°S).

Answer:

the prime meridian