If $$mx^{m} - nx^{n} = 0$$ then what is the value of $$\frac{1}{x^{m} + x^{n}} + \frac{1}{x^{m} - x^{n}}$$ in terms of $$x^{n}$$

A

$$\frac{2mn}{x^{n}\left(n^{2} + m^{2}\right)}$$

B

$$\frac{2m}{x^{n}\left(m^{2} - n^{2}\right)}$$

C

$$\frac{2mn}{x^{n}\left(n^{2} - m^{2}\right)}$$

D

$$\frac{2mn}{x^{n}\left(m^{2} - n^{2}\right)}$$