A car is moving towards a high cliff. The car driver sounds a horn of frequency 'f'. The reflected sound heard by the driver has a frequency 2f. If 'v' be the velocity of sound then the velocity of the car, in the same velocity units, will be -

Question

( A ) $V/2$
( B ) $V/3$
( C ) $V/4$
( D ) $V/\sqrt{2}$