If $\mathrm{\gamma }=\frac{{\mathrm{C}}_{\mathrm{P}}}{{\mathrm{C}}_{\mathrm{V}}},{\mathrm{C}}_{\mathrm{P}}$ being the molar specific heat of a gas at  constant pressure and $C_V$ its molar specific heat at constant volume, number of degrees of freedom of a molecule of gas can be expressed as:

• A

  $\frac{5}{2}(\mathrm{\gamma }-1)$

• B

  $\frac{7\mathrm{\gamma }-1}{3\mathrm{\gamma }-1}$

• C

  $\frac{3}{2}\left(\mathrm{\gamma }-1\right)$

• D

  $\frac{2}{\mathrm{\gamma }-1}$