The set of circles on the Earth's surface that are parallel to the equator is called:

• A. Meridians.
• B. Poles.
• C. Parallels of latitude.
• D. Great circles.

Answer: (C)

Parallels of latitude are the circles on the Earth's surface that run east-west and stay at a constant distance from the equator. They form a family of circles around the globe, all parallel to the equator, and are used to measure how far north or south you are. The equator itself is one of these parallels. Other parallels lie in planes that don’t pass through Earth’s center, so they are smaller circles rather than through-center great circles. Meridians, in contrast, run north-south and meet at the poles, and great circles are circles formed by planes that cut through the center (with the equator being the primary example).