Which one of the following statements is true for the relation $F=\frac{\mathrm{Gm}_1 \mathrm{~m}_2}{\mathrm{r}^2}$ ? (All symbols have their usual meanings)

• A

  The quantity $G$ depends on the local value of $g$, acceleration due to gravity
• B

  The quantity G is greatest at the surface of the Earth
• C

  The quantity G is used only when earth is one of the two masses
• Correct answer
  D

  The quantity G is a universal constant

Hence, the correct answer is option: 'D'.