A bar of square section of area $$a^2$$ is held such that one of its diameters is vertical. The maximum shear stress will develop at a depth h where h is

A

$$\frac{(2 \surd 3)}{4}$$

B

$$\frac{(3 \surd 2)}{4}$$

C

$$\frac{2}{\surd 3}$$

D

$$\frac{\surd 3}{4}$$