$$\int_{0}^{a} \frac{x^{4}dx}{(a^{2} + x^{2})^4}$$=

A

$$\frac{1}{16}a^{3}(\frac{\pi}{4} - \frac{1}{3})$$

B

$$\frac{1}{16}a^{3}(\frac{\pi}{4} + \frac{1}{3})$$

C

$$\frac{1}{16a^{3}}(\frac{\pi}{4} - \frac{1}{3})$$

D

$$\frac{1}{16a^{3}}(\frac{\pi}{4} + \frac{1}{3})$$