A ball of mass m moving with a speed `2v_0` collides head-on with an identical ball at rest. If e is the coefficient of restitution, then what will be the ratio of velocity of two balls after collision?
A. `(1-e)/(1+e)`
B. `(e-1)/(e+1)`
C. `(1+e)/(1-e)`
D. `(e+1)/(e-1)`
