Which of the following is an equation of state for an adiabatic process?
(i) ${\mathrm{PV}}^{\mathrm{\gamma }}=\mathrm{constt}.$ 
(ii) $\mathrm{P}/{\mathrm{\rho }}^{\mathrm{\gamma }}=\mathrm{constt}.$
(iii) ${\mathrm{TV}}^{\mathrm{\gamma }-1}=\mathrm{constt}.$.
(iv) ${\mathrm{T}}^{\mathrm{\gamma }}/{\mathrm{P}}^{\mathrm{\gamma }-1}=\mathrm{constt}.$.

• A

  (iii, iv)

• B

  (i, ii, iii)

• C

  (i, iii, iv)

• D

  (i, ii, iii, iv)