Q ​A particle starts from rest at a distance R from the centre and along the axis of 
a fixed ring of radius R & mass M. Its velocity at the centre of the ring is: 

 $$\begin{gathered} A) \sqrt{\frac{\sqrt{2}GM}{R}} \\ B)\sqrt{\frac{2GM}{R}} \\ C\left)\sqrt{\left(1-\frac{1}{\sqrt{2}}\right)\frac{GM}{R}} \\ D\right) \sqrt{\left(2-\sqrt{2}\right)\frac{GM}{R}} \end{gathered}$$