$A$ motorcyclist moving with a velocity of $72\, km/h$ on a flat road takes a turn at a point where the radius of curvature of the road is $20\, m$. The acceleration due to gravity is $10\, m/s^2$. In order to avoid skidding,he must not bend with respect to the vertical plane by an angle greater than

• A
  $\theta = \tan^{-1}(6)$
• B
  $\theta = \tan^{-1}(2)$
• C
  $\theta = \tan^{-1}(25.92)$
• D
  $\theta = \tan^{-1}(4)$