Which equation has a center at (2, 1) and a point on the circle of (2, -3)?
a. (x + 2)² + (y + 1)² = 16
b. (x - 2)² + (y - 1)² = 4
c. (x - 2)² + (y - 1)² = 16
d. (x + 2)² + (y + 1)² = 4