Consider the following equations:(a) A1v1 = A2v2(b) \(\frac{{\partial u}}{{\partial x}} + \frac{{\partial v}}{{\partial y}} = 0\)(c) \(\mathop \smallint \limits_{\rm{s}} {\rm{pV}}.{\rm{dA}} + \frac{\partial }{{\partial {\rm{t}}}}\mathop \smallint \limits_{\rm{v}} {\rm{pdV}} = 0\)(d) \(\frac{1}{r}\;\frac{\partial }{{\partial r}}\left( {r{v_r}} \right) + \frac{\partial }{{\partial z}}\left( {{v_z}} \right) = 0\)Which of the above equations are forms of continuity equations? (Where u, v are velocities and V is volume)

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