The locus of the point $z=x+iy$ satisfying $\bigg|\large\frac{z-2i}{z+2i} \bigg|$$=1$ is

Question

$$\begin {array} {1 1} (a)\;x-axis & \quad (b)\;y-axis \\ (c)\;y=2 & \quad (d)\;x=2 \end {array}$$