A motor cyclist moving with a velocity of 72 km/hour on a flat road takes a turn on the road at a point where the radius of curvature of the road is 20 meters . The acceleration due to gravity is `10m//sec^(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)`