$A$ rectangular block of mass $m$ and cross-sectional area $A$ floats on a liquid of density $\rho$. It is given a small vertical displacement from equilibrium,and it starts oscillating with frequency $n$. The frequency $n$ is equal to (where $g$ is the acceleration due to gravity):

• A
  $\frac{1}{2 \pi} \sqrt{\frac{A \rho g}{m}}$
• B
  $2 \pi \sqrt{\frac{A \rho g}{m}}$
• C
  $\frac{1}{2 \pi} \sqrt{\frac{m}{A \rho g}}$
• D
  $2 \pi \sqrt{\frac{m}{A \rho g}}$