Gravitational force is the force of attraction between two objects with mass. It is one of the fundamental forces in nature and plays a significant role in determining the motion and behavior of celestial bodies, as well as everyday objects on Earth. The force of gravity is responsible for keeping planets in orbit around the sun, objects falling to the ground when dropped, and many other phenomena we observe in our daily lives.

The force of attraction between two point masses can be mathematically described using Newton's law of universal gravitation. According to this law, the gravitational force between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. Mathematically, it can be expressed as:

F = G * (m1 * m2) / r^2

where F is the gravitational force, G is the universal gravitational constant, m1 and m2 are the masses of the two objects, and r is the distance between their centers.

In the given question, we have two unit point masses separated by a unit distance. This means that both masses are equal to 1 and the distance between them is also equal to 1. Plugging these values into the equation, we get:

F = G * (1 * 1) / 1^2
F = G

Therefore, in this specific scenario, the gravitational force between the two unit point masses separated by a unit distance is simply equal to the universal gravitational constant, denoted by G.

The universal gravitational constant, denoted by G, is a fundamental constant in physics. Its value is approximately 6.67430 × 10^-11 N*m^2/kg^2. It represents the proportionality factor in Newton's law of universal gravitation and is used to calculate the gravitational force between any two objects with mass.

To summarize, the force of attraction between two unit point masses separated by a unit distance is equal to the universal gravitational constant, denoted by G. This force is determined by Newton's law of universal gravitation, which describes the gravitational force between two objects as a function of their masses and the distance between them.

Option D is correct