All the particles of a body are situated at a distance r from the origin.the distance of centre of mass of body from origin will be-
(a)=r
(b)< or = r

All the particles of a body are situated at a distance r from the origin.the distance of centre of mass of body from origin will be-
(a)=r
(b)< or = r

If you try a couple of examples you should be able to get this. What if there is only one particle, located at x = r? What if there are two particles, one located at x = -r and the other at x=r? What do you conclude?