Four similar particles of mass m are orbiting in a circle of radius r in the same angular direction because of their mutual gravitational attractive force. Then, velocity of a particle is given by

• A. \[{{\left[ \frac{Gm}{r}\left( \frac{1+2\sqrt{2}}{4} \right) \right]}^{\frac{1}{2}}}\]            
• B. \[\sqrt{\frac{Gm}{r}}\]
• C. \[\sqrt{\frac{Gm}{r}}\left( 1+2\sqrt{2} \right)\]    
• D. \[a{{\left[ \frac{1}{2}\frac{Gm}{r}\left( \frac{1+2\sqrt{2}}{2} \right) \right]}^{\frac{1}{2}}}\]