A bent tube of uniform cross-section area $A$ has a non-viscous liquid of density $\rho$. The mass of liquid in the tube is $m$. The time period of oscillation of the liquid is :
(a) $2 \pi \sqrt{\frac{m}{\rho g A}}$
(b) $2 \pi \sqrt{\frac{m}{2 \rho g A}}$
(c) $2 \pi \sqrt{\frac{2 m}{\rho g A}}$
(d) None of these