During adiabatic process pressure P versus density $\mathrm{\rho }$ equation is:

• A

  ${\mathrm{P\rho }}^{\mathrm{\gamma }}= \mathrm{constant}$

• B

  ${\mathrm{P\rho }}^{-\mathrm{\gamma }} = \mathrm{constant}$

• C

  ${\mathrm{P}}^{\mathrm{\gamma }}{\mathrm{\rho }}^{1+\mathrm{\gamma }} = \mathrm{constant}$

• D

  ${\mathrm{P}}^{\frac{1}{\mathrm{\gamma }}}{\mathrm{\rho }}^{\mathrm{\gamma }} = \mathrm{constant}$