For the case of a slender column oflength Land flexural rigidity EI built in at its base and free at the top, the Eulers critical buckling load is

A

$$\frac{4 \pi^2 EI}{L^2}$$

B

$$\frac{2 \pi^2 EI}{L^2}$$

C

$$\frac{\pi^2 EI}{L^2}$$

D

$$\frac{\pi^2 EI}{4L^2}$$