If a circle passes through the point (a, b) and cuts the circle $x^2+y^2=4$ orthogonally, then the locus of its centre is

Question

( A ) $2ax-2by +(a^2+b^2+4)$=0$
( B ) $2ax+2by -(a^2+b^2+4)$=0$
( C ) $2ax+2by +(a^2+b^2+4)$=0$
( D ) $2ax-2by -(a^2+b^2+4)$=0$