If \(D\) is the diameter of wheel and \(d_{1}\) and \(d_{2}\) diameters of two axles, then velocity ratio is

(a) \(\frac{D}{d_{2}-d_{1}}\)

(b) \(\frac{D}{2\left(d_{2}-d_{1}\right)}\)

(c) \(\frac{2 D}{d_{2}-d_{1}}\)

(d) \(\frac{2 D}{d_{2}+d_{1}}\)