For a = 0, the value of d (maximum value of $$\rho$$ as shown in the figure) is

A

$$\frac{3Ze}{4 \pi R^3}$$

B

$$\frac{3Ze}{\pi R^3}$$

C

$$\frac{4Ze}{3 \pi R^3}$$

D

$$\frac{Ze}{3 \pi R^3}$$