For a column of length L is fixed at both ends, corresponding Euler’s critical load is

A

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

B

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

C

$$\frac {3\pi^2 EI}{L^2}$$

D

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