Question

Which among the following relations is/are valid ONLY for reversible process undergone by a pure substance?                                                                                                                                                                   

      (a) $\delta$Q = du +$\delta$W

      (b) T dS = dU + $\delta$W

      (c) T dS = dU + p dv

      (d) $\delta$Q = p dV + dU