A solid sphere of uniform density and radius 4 units is located with its center at origin O. Two spheres of equal radii/ units with their center $A(-2,0,0)$ and $B(2,0,0)$ respectively are taken out of the solid leaving behind cavities as shown Then

Question

 

a) The gravitational field due to this object at orgin is zero

b) The gravitational field at B(2,0,0) is zero

c)The gravitational potential is same at all points on the circle. $y^2+z^2=36$

d) The gravitational potential is same at all points on the circle. $y^2+z^2=4$