Correct Answer - D
When they are at infinite distance, their P.E. = 0 and K.E. = 0 and gravitational force `F=(Gm_(1)m_(2))/(d^(2))` is also zero.
When the distance of separation between the two masses becomes r,
(i) their total energy is finite
(ii) force of attraction between them is finite and
(iii) the centre of mass of the system is at rest because, initially the masses are at rest and there is no external force acting on the system. Thus (a), (b) and (c ) are true and the correct choice is (d).