When objects are moved further apart from each other, the force of gravity a decreases. b stays the same. C increases. d decreases at first and then increases.

## Step 1<br />The problem is about the force of gravity between two objects. According to Newton's law of universal gravitation, the force of gravity between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. This relationship is mathematically represented as:<br />### \(F = G \frac{m_1 m_2}{r^2}\)<br />where \(F\) is the gravitational force, \(G\) is the gravitational constant, \(m_1\) and \(m_2\) are the masses of the two objects, and \(r\) is the distance between the centers of the two objects.<br /><br />## Step 2<br />From the formula, it can be seen that as the distance \(r\) between the two objects increases, the denominator of the fraction becomes larger, which means the overall force \(F\) decreases. This is because the force of gravity is inversely proportional to the square of the distance between the two objects.