A conductor of length 'L' is connected to a battery of emf 'E'. The drift velocity of electron in the conductor is ' $v_{d}$ '. The drift velocity of electron in the conductor on stretching it four times, to length 4 L keeping emf 'E' constant will be:

$4 v_d$ $0.25 v_d$ $0.5 v_d$ $2 v_{d}$

$0.25 v_d$

The correct answer is Option (2) → $0.25 v_d$