A thin uniform rigid bar of length L and mass M is hinged at point O, located at a distance of L/3 from one of its ends. The bar is further supported using spring, each of stiffness k, located at the two ends. A particle of mass \(m = \frac{M}{4}\) is fixed at one end of the bar, as shown in the figure. For small rotations of the bar about O, the natural frequency of the system is

• A. \(\sqrt {\frac{{5k}}{M}} \)
• B. \(\sqrt {\frac{{5k}}{{2M}}} \)
• C. \(\sqrt {\frac{{3k}}{{2M}}} \)
• D. \(\sqrt {\frac{{3k}}{M}} \)