Let $\mathrm{A}=(2,0,-1), \mathrm{B}=(1,-2,0), \mathrm{C}=(1,2,-1)$ and $\mathrm{D}=(0,-1,-2)$ be four points. If $\theta$ is the acute angle between the plane determined by $A, B, C$ and the plane determined by $\mathrm{A}, \mathrm{C}, \mathrm{D}$, then $\tan \theta=$

• A

  $\sqrt{\frac{14}{5}}$
• B

  $\frac{3}{\sqrt{14}}$
• Correct answer
  C

  $\frac{3}{\sqrt{5}}$
• D

  $\frac{\sqrt{5}}{3}$

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