Which one of the following represents equilibrium of a static fluid? (Symbols have the usual meaning)

• A. \[\frac{dp}{dz}=-\frac{\rho }{g}\]                      
• B. \[\frac{dp}{g}\,=\,-\,\frac{dz}{\rho }\]
• C. \[\rho \,dp=-\frac{dz}{g}\]                      
• D. \[\frac{dp}{\rho }=-g\,dz\]