A motorcyclist of mass m is to negotiate a curve of radius r with a speed v. The minimum value of the coefficient of friction so that this negotiation may take place safely, is [Haryana CEE 1996]

• A.                         \[{{v}^{2}}rg\]                    
• B.                         \[\frac{{{v}^{2}}}{gr}\]            
• C.                         \[\frac{gr}{{{v}^{2}}}\]                 
• D.                         \[\frac{g}{{{v}^{2}}r}\]