A great circle crosses the equator at 173°E. It will also cross the equator at what other longitude?

Correct Answer: Option D — 7°W

A great circle is the intersection of a sphere and a plane passing through its center. Because it is a complete circle around the Earth, it must intersect the equator at two points exactly 180 degrees apart. 173°E plus 180° equals 353°, which is equivalent to 7°W longitude.