The equation of the sphere concentric with the sphere `2x^2+2y^2+2z^2-6x+2y-4z=1` and double its radius is (A) `x^2+y^2+z^2-x+y-z=1` (B) `x^2+y^2+z^2-6x+2y-4z=1` (C) `2x^2+2y^2+2z^2-6x+2y-4z-15=0` (D) 2x^2+2y^2+2z^2-6x+2y-4z-25=0`