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

• A

  $\frac{2 x}{x^4+2 x^2+2}$
• Correct answer
  B

  $-\frac{2 x}{x^4-2 x^2+2}$
• C

  $\frac{2 x}{x^4-2 x^2+2}$
• D

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

Hence, the correct answer is option: 'B'.