$A$ closed water tank has a cross-sectional area $A$. It has a small hole at a depth of $h$ from the free surface of the water. The radius of the hole is $r$ such that $r \ll \sqrt{\frac{A}{\pi}}$. If $p_o$ is the pressure inside the tank above the water level and $p_a$ is the atmospheric pressure,the rate of flow of the water coming out of the hole is ($\rho$ is the density of water).

• A
  $\pi r^2 \sqrt{2 g h}$
• B
  $\pi r^2 \sqrt{2 g h+\frac{2\left(p_o-p_a\right)}{\rho}}$
• C
  $\pi r^2 \sqrt{2 g H}$
• D
  $\pi r^2 \sqrt{g h+\frac{2\left(p_0-p_a\right)}{\rho}}$