If a circle passes through the point (a, b) and cuts the circle x2 + y2 = 4 orthogonally, then the locus of its centre is
(a) 2ax+ 2 by + (a2 + b2 + 4) = O
(b) 2ax+ 2by - (a2 + b2 + 4) = O
(c) 2ax - 2by + (a2 + b2 + 4) = O
(d) 2ax - 2 by - (a2 + b2 + 4) = O
