The correct answer is A) The intersection of a plane passing through the center of a sphere. A great circle is defined as the intersection of a plane passing through the center of a sphere. This is the largest possible circle that can be drawn on the surface of a sphere. Great circles represent the shortest distance between any two points on the sphere, making them important for navigation. The other options are incorrect because: B) is describing a rhumb line or loxodromic curve, C) is not the definition of a great circle, and D) is describing the smallest possible circle on a sphere, which is not the definition of a great circle.