The value of $\int_{\pi / 6}^{\pi / 3} \frac{\ln (\tan x)}{\sin ^4 x+\cos ^4 x} d x$ is

• A

  $\frac{\pi}{2}$
• B

  $\frac{\pi}{4}$
• Correct answer
  C

  0
• D

  $\pi$

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