The third proportional of a and $$\frac{b^{4}}{4a}$$ is:

A

$$\frac{b^{8}}{16a^{2}}$$

B

$$\frac{b^{8}}{8a^{2}}$$

C

$$\frac{b^{8}}{8a^{3}}$$

D

$$\frac{b^{8}}{16a^{3}}$$