The correct answer is
D. d
The distance.
In fact, the gravitational force between two objects is given by:
[tex]F=G\frac{m_1 m_2}{d^2}[/tex]
where
G is the gravitational constant
m1 and m2 are the masses of the two objects
d is their distance
From the formula, we see that the only quantity that is squared is the distance, d.
