Which equation has a center at (2, 1) and a point on the circle of (2, –3)?

A circle with center (h, k) has equation (x − h)² + (y − k)² = r². Using the center (2, 1) gives (x − 2)² + (y − 1)². The point (2, −3) is 4 units from the center, so r² = 4² = 16; choice C matches.

AI-written and checked against the verified answer.