Find the equation of the circle with centre (0,2) and radius 2

Question

$\begin {array} {1 1} (A)\;x^2-y^2-4y=0 & \quad (B)\;x^2+y^2-4y=0 \\ (C)\;x^2-y^2+4y=0 & \quad (D)\;x^2+y^2+4y=0 \end {array}$