The volume of one mole of the gas is changed from $V$ to $2 V$ at constant pressure $p$. If $\gamma$ is the ratio of specific heats of the gas, change in internal energy of the gas is

• A

  $\frac{r . p V}{\gamma-1}$
• B

  $\frac{r}{\gamma-1}$
• C

  $p V$
• Correct answer
  D

  $\frac{p V}{\gamma-1}$

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