Which of the above equations are forms of continuity equations?

Question

Consider the following equations:

1. $A_{1}v_{1} = A_{2}v_{2}$

2. $\frac{\partial u}{\partial x}+\frac{\partial v}{\partial y} = 0$

3. $\int_{s}^{}\rho vdA + \frac{\partial }{\partial t}(\int_{v}^{}\rho dV) = 0$

4.  $\frac{1}{r}\frac{\partial }{\partial r}(rv_{t}) + \frac{\partial }{\partial z}(V_{z}) = 0$

Which of the above equations are forms of continuity equations? (Where u, v are velocities and V is volume)

(a) 1 only                     (b) 1 and 2

(c) 2 and 3                   (d) 3 and 4