If r represents the radius of the orbit of a planet of mass m moving around the Sun of mass M, the orbital velocity of the planet is given by:

The correct answer is:

Mass of the Sun = M, Mass of the planet = m, The centripetal acceleration of the planet = a_c
Fg = Fc  = ma_c
GMm/r² = mv²/r
Hence the orbital velocity v for the planet is given by
V = √GM/r
Where G = Universal Gravitational Constant
V² = GM/r