A rectangular hyperbola whose cetre is C is cut by any circle of radius r in four points $P,Q,R$ and S. Then $CP^2+CQ^2+CR2+CS^2$ is equal to.

Question

$\begin{array}{1 1}(A)\;r^2 \\(B)\;2r^2 \\(C)\;3\;r^2 \\(D)\;4\;r^2 \end{array}$