The value of $$\frac{1}{1-x}+\frac{1}{1+x}+\frac{2}{1+x^2}+\frac{4}{1+x^4}$$

A

$$\frac{8}{1-x^8}$$

B

$$\frac{4x}{1+x^2}$$

C

$$\frac{4}{1-x^6}$$

D

$$\frac{4}{1+x^4}$$