The force of attraction between two objects of mass 'M' and 'm' separated by a distance 'd' is proportional to the:

Gravity is the universal force of attraction that acts between all matter. It is the weakest known natural force. According to the Law of Universal Gravitation, every mass in the universe attracts every other mass through a force acting on a straight line between the centres of mass of both points. The force is proportional to the product of the objects' masses and inversely proportional to the square of their distance apart.

$\mathrm{F} =\mathrm{G}\frac{\mathrm{Mm}}{{\mathrm{R}}^2}$

Here G is the universal gravitational constant, M  and m  are masses and r is the distance between two masses. The Law applies to all objects with masses, no matter how large or small.

The force of attraction between two objects of mass M  and m  separated by a distance d is directly proportional to the Product of the masses of the objects, $\mathrm{M}\times \mathrm{m}$.  As a result, option B is correct.