The maximum deflection of a simply supported beam of span L carrying an isolated load at the center of the span, flexural rigidity being EI is

A

$$\frac{WL^{3}}{3EI}$$

B

$$\frac{WL^{3}}{8EI}$$

C

$$\frac{WL^{3}}{24EI}$$

D

$$\frac{WL^{3}}{48EI}$$