Solve this following

Mark $(\sqrt{ })$ against the correct answer in the following:

If $y=\sqrt{\frac{1+\tan x}{1-\tan x}}$ then $\frac{d y}{d x}=$ ?

A. $\frac{1}{2} \sec ^{2} x \cdot \tan \left(x+\frac{\pi}{4}\right)$

B. $\frac{\sec ^{2}\left(x+\frac{\pi}{4}\right)}{2 \sqrt{\tan \left(x+\frac{\pi}{4}\right)}}$

C. $\frac{\sec ^{2}\left(\frac{x}{4}\right)}{\sqrt{\tan \left(x+\frac{\pi}{4}\right)}}$

D. none of these