If p and τ are the net pressure and net shear stress acting on an infinitesimally small element (volume dx dy dz) moving along with the flow (velocity \(\vec{V}\)), what is the net work done on the system?

• A. \(\rho (\nabla .(p\vec{V} )+\nabla .(τ.\vec{V}))\)
• B. \(((p\vec{V})+(\tau.\vec{V}))dx \,dy \,dz\)
• C. \(\rho(\nabla.(p\vec{V})+\nabla.(\tau.\vec{V})) dx \,dy \,dz\)
• D. \((\nabla .(p)+\nabla.(\tau))dx \,dy \,dz\)