Four particles, each of mass M and equidistant from each other, move along a circle of radius R under the action of their mutual gravitational attraction. The speed of each particle is:
A. `(GM)/(R )`
B. `sqrt(2sqrt(2)(GM)/(R ))`
C. `sqrt((GM)/(R)(2sqrt(2) + 1))`
D. `sqrt((GM)/(R)(2sqrt(2) + 1)/(4))`