A line of latitude that is not the equator is:

• A. A great circle.
• B. The equator.
• C. A meridian.
• D. A small circle parallel to the equator.

Answer: (D)

A line of latitude that isn’t the equator is a small circle that runs parallel to the equator. Latitudes are circles on the globe formed by the intersection of Earth with planes parallel to the equatorial plane. The equator itself is special because its plane passes through Earth’s center, making it a great circle—the largest possible circle on the sphere and the only latitude that is a great circle. Any other latitude lies in a plane offset from the center, so its circle is smaller than the equator—the small circle that remains parallel to it.

A meridian, in contrast, is a line of longitude running from pole to pole, not a latitude. The equator is the single latitude that is also a great circle. Hence, a latitude that is not the equator is correctly described as a small circle parallel to the equator.