A suitable unit for gravitational constant is

The correct answer is Newton meter² kg⁻².

To find the suitable unit for the universal gravitational constant ($G$), we can use Newton's law of universal gravitation. According to this law, the gravitational force ($F$) between two masses ($m_1$ and $m_2$) separated by a distance ($r$) is given by the formula:
$F=\frac{G{m}_1{m}_2}{r^2}$

To find the unit of the gravitational constant $G$, we can rearrange the formula to solve for $G$:
$G=\frac{F{r}^2}{m_1{m}_2}$

Now, let's substitute the standard SI units for each of the variables in this equation:
1. Force ($F$) is measured in Newtons ($N$).
2. Distance ($r$) is measured in meters ($m$), so $r^2$ has the unit meter² ($m^2$).
3. Masses ($m_1$ and $m_2$) are measured in kilograms ($\mathrm{kg}$), so their product $m_1{m}_2$ has the unit kg × kg = kg².

Substituting these units into our rearranged equation for $G$ gives:
Unit of $G=\frac{\mathrm{Newton}\times {\mathrm{meter}}^2}{{\mathrm{kg}}^2}$

Expressing this division using negative exponents, we get:
Unit of $G={\text{Newton meter}}^2{\text{kg}}^{-2}$

Therefore, a suitable unit for the gravitational constant is Newton meter² kg⁻².