Final answer:
The greatest gravitational force between two objects occurs when both objects have a large mass and the distance between them is small, as gravitational force is directly proportional to the mass product and inversely proportional to the distance squared.
Step-by-step explanation:
The question is inquiring about the conditions that result in the greatest gravitational force between two objects. According to the law of universal gravitation, the gravitational force is directly proportional to the product of the masses of the two objects and inversely proportional to the square of the distance between them. This means that the gravitational force will be greatest when the masses of both objects are large and the distance between them is small.
Therefore, the correct answer is b. when mass is large and the objects are close together. This is because a large mass for both objects increases the product of the masses, and a short distance means the denominator in the inverse square law is smaller, which together result in a larger gravitational force. Statements suggesting that gravitational force is directly proportional to the sum of the squares of the masses or that mass and force are unrelated are incorrect. It's also incorrect to assume that the strong attractive force in question acts at all distances or is related to the energy levels of the particles.