The range of $\operatorname{Sin}^{-1} x+\operatorname{Cos}^{-1} x+\operatorname{Tan}^{-1} x$ is

• A

  $\left(0, \frac{\pi}{2}\right)$
• B

  $(0, \pi]$
• Correct answer
  C

  $\left[\frac{\pi}{4}, \frac{3 \pi}{4}\right]$
• D

  $[0, \pi]$

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