$A$ car of mass $m$ moves on a banked road having radius $r$ and banking angle $\theta$. To avoid slipping from the banked road,the maximum permissible speed of the car is $v_0$. The coefficient of friction $\mu$ between the wheels of the car and the banked road is:

• A
  $\mu=\frac{v_0^2+r g \tan \theta}{r g-v_0^2 \tan \theta}$
• B
  $\mu=\frac{v_0^2+r g \tan \theta}{r g+v_0^2 \tan \theta}$
• C
  $\mu=\frac{v_0^2-r g \tan \theta}{r g+v_0^2 \tan \theta}$
• D
  $\mu=\frac{v_0^2-r g \tan \theta}{r g-v_0^2 \tan \theta}$