Which of the following equations are forms of continuity equations? (\[\overrightarrow{V}\]is the velocity and \[\forall \] is volume) 1. \[{{A}_{1}}{{\overrightarrow{V}}_{1}}={{A}_{2}}\overrightarrow{{{V}_{2}}}\] 2. \[1\frac{du}{\partial x}+\frac{dv}{\partial y}=0\] 3. \[\int\limits_{S}{\rho \overrightarrow{V}\,.\,dA+\int\limits_{\forall }{\rho \,d\forall =0}}\] 4. \[\frac{1}{r}\,\,\frac{\partial \,\left( r{{v}_{r}} \right)}{\partial r}+\frac{\partial {{v}_{z}}}{\partial z}=0\] Select the correct answer using the codes below: Codes:

• A. 1, 2, 3 and 4                 
• B. 1 and 2
• C. 3 and 4            
• D. 2, 3 and 4