If $$\log_{cos  x} (\sin  x) + \log_{\sin  x}(cos  x) = 2$$, then the value of x is

A

$$2n\pi + \frac{\pi}{4}$$, n is an interger

B

$$n\pi + \frac{\pi}{4}$$, n is an interger

C

$$\frac{n\pi}{4} + \frac{\pi}{4}$$, n is an interger

D

$$\frac{n\pi}{4}$$, n is an interger