What is the equation of a circle with center (-2,3) and radius 4?
A. (x + 2)^2 +(y-3)^2 = 4
B. (x-2)^2 +(y +3)^2= 16
C. (x + 2)^2 + (y - 3)^2 = 16
D. (x+2)^2- (y - 3)^2 - 16