A point particle is held on the axis of a ring of mass $$m$$ and radius $$r$$ at a distance $$r$$ from its centre $$C$$. When released, it reaches $$C$$ under the gravitational attraction of the ring. Its speed at $$C$$ will be

A

$$\sqrt{\frac{2Gm}{r}(\sqrt{2}-1)}$$

B

$$\sqrt{\frac{Gm}{r}}$$

C

$$\sqrt{\frac{2Gm}{r}\left(1 - \frac{1}{\sqrt{2}}\right)}$$

D

$$\sqrt{\frac{2Gm}{r}}$$