Which statement about great circles is true?

• A. They are always identical to lines of latitude.
• B. They divide the Earth into two equal halves.
• C. They pass through the poles.
• D. They are only found at the equator.

Answer: (B)

Great circles are the largest circles you can draw on a sphere, formed by the intersection of the sphere with a plane that passes through the Earth's center. Because that plane cuts the globe into two equal halves, any great circle divides the surface into two equal hemispheres. That universal property is what makes this statement true.

In contrast, lines of latitude are circles in planes parallel to the equator; only the equator itself is a great circle, so great circles aren’t identical to lines of latitude in general. Some great circles, like those corresponding to meridians, do pass through the poles, but not all great circles go through the poles. And great circles aren’t limited to the equator—they can exist at many orientations around the globe.