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

• Correct answer
  A

  $-\sqrt{\frac{y-y^2}{x-x^2}}$
• B

  $-\sqrt{\frac{1-y^2}{1-x^2}}$
• C

  $-\sqrt{\frac{1-y}{1-x}}$
• D

  $-\sqrt{\frac{x-y}{x+y}}$

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