<Dl> <Dd> d S> δ Q T (closed system, actually possible, irreversible process). (\ displaystyle \ mathrm (d) S> (\ frac (\ delta Q) (T)) \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, (\ text ((closed system, actually possible, irreversible process).))) </Dd> </Dl> <Dd> d S> δ Q T (closed system, actually possible, irreversible process). (\ displaystyle \ mathrm (d) S> (\ frac (\ delta Q) (T)) \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, (\ text ((closed system, actually possible, irreversible process).))) </Dd> <P> This is because a general process for this case may include work being done on the system by its surroundings, which must have frictional or viscous effects inside the system, and because heat transfer actually occurs only irreversibly, driven by a finite temperature difference . </P> <P> The zeroth law of thermodynamics in its usual short statement allows recognition that two bodies in a relation of thermal equilibrium have the same temperature, especially that a test body has the same temperature as a reference thermometric body . For a body in thermal equilibrium with another, there are indefinitely many empirical temperature scales, in general respectively depending on the properties of a particular reference thermometric body . The second law allows a distinguished temperature scale, which defines an absolute, thermodynamic temperature, independent of the properties of any particular reference thermometric body . </P>

Which statement best describes the second law of thermodynamics