Which equation is the equation of a circle with a diameter of 20 cm and center at (-3, 6)?

A. (x-3)^2 + (y+6)^2 = 400
B. (x-3)^2 + (y+6)^2 = 100
C. (x+3)^2 + (y-6)^2 = 100
D. (x+3)^2 + (y-6)^2 = 400