Answer: The object having 8 kg mass will exert the maximum gravitational force on the box.
Explanation: Gravitational force is defined as the attractive force acting between any two bodies having masses
and are 'r' distance apart.
This force is directly proportional to the product of the two masses and inversely proportional to the square of the distance between them.
Mathematically,

where,
F = gravitational force
= masses of the two bodies
r = distance between them
G = universal gravitational constant.
- We are given a box and force is acting on it.
Let the mass of box be

In order to have the greatest gravitational force, the mass of the object should be also be the greatest because mass of box is fixed.
So, the object having mass 8 kg will exert greatest gravitational force on the box.