An ideal gas undergoes a quasi-static, reversible process in which its molar heat capacity $C$ remains constant. If during this process the relation of pressure $P$ and volume $V$ is given by $PV^n = \text{constant}$, then $n$ is given by (Here $C_P$ and $C_V$ are molar specific heat at constant pressure and constant volume, respectively).

• A
  $n = \frac{C - C_V}{C - C_P}$
• B
  $n = \frac{C_P}{C_V}$
• C
  $n = \frac{C - C_P}{C - C_V}$
• D
  $n = \frac{C_P - C}{C - C_V}$