Option 1 -> This is the definition of the universal gravitational constant (G): the force between two unit masses at unit distance.
Option 2 -> This is the acceleration experienced by objects near Earth's surface (~9.8 m/s²), not a force between unit masses.
Option 3 -> This is the work done per unit mass to bring an object from infinity to a point, measured in J/kg.
Option 4 -> This is the force per unit mass at a point in space (N/kg), not the force itself between specific masses.
Hence, Universal gravitational constant -> By Newton's law F = G(m₁m₂)/r², when m₁ = m₂ = 1 and r = 1, the force F = G. This is precisely how the constant G is defined in physics -> correct