The natural frequency of a simply supported beam of length l with mass M at its centre , flexual rigidity EI and negligable beam mass is

A

$$\frac{1}{2 \pi} \sqrt{\frac{48EI}{ml^{3}}}$$

B

$$\frac{1}{2 \pi} \sqrt{\frac{3EI}{ml^{3}}}$$

C

$$\frac{1}{2 \pi} \sqrt{\frac{EI}{ml^{3}}}$$

D

None of the above