Correct Answer - B
The distance of `CM` from the ring centre `O`
`x+(3m(0)+m(r))/(3m+m)=r/4`
We can apply torque equation about point of contact at the ring is rolling.
`tau_(P)=I_(P)alpha`
`4mg(r/4)=[(3mr^(2)+mr^(2))m(AP)^(2)]alpha` ltbr gt `implies mgr=[4mr^(2)+m(sqrt(2)r)^(2)]alpha`
`implies mgr=6mr^(2)alphaimplies g/(6r)`