The 45-degree-north line of latitude is:

• A. A great circle.
• B. The equator.
• C. A circle formed by a plane through the center.
• D. A small circle parallel to the equator.

Answer: (D)

Lines of latitude are circles on the globe formed by intersecting the Earth with planes that are parallel to the equatorial plane. The equator itself is special because its plane passes through the Earth's center, making it a great circle. All other latitudes, like 45 degrees north, come from planes offset from the center, so their circles are smaller than the equator. The 45°N line is therefore a small circle that runs parallel to the equator (its radius is R cos 45°). This is why it is not a great circle.

If you’re charting, you’ll see latitude lines other than the equator drawn as these smaller circles parallel to the equator.