Validity of work done equation in the open system - GATE ME '08

In a steady state steady flow process taking place in a device with a single inlet and a single outlet, the work done per unit mass flow rate is given by W=−∫ vdp, where v is the specific volume and P is the pressure. The expression for ′W′ given above A. is valid only if the process is both reversible and adiabatic B. is valid only if the process is both reversible and isothermal C. is valid for any reversible D. is incorrect, it must be W=∫pdv