If $C_p$ and $C_v$ are molar specific heats of an ideal gas at constant pressure and volume respectively,if $\gamma$ is the ratio of the two specific heats and $R$ is the universal gas constant,then $C_p$ is equal to

• A
  $\frac{R \gamma}{\gamma-1}$
• B
  $\gamma R$
• C
  $\frac{1+\gamma}{1-\gamma}$
• D
  $\frac{R}{\gamma-1}$