Correct option is D
Relative speed (Sr) = 13 km/h - 12 km/h = 1 km/h
Time taken (T) = 300 m / (5/18 m/s) = 300 * (18/5) seconds = 1080 seconds
Distance run by thief (Dt) = Speed of thief * Time taken
D = 12 km/h = 12 * (1000/3600) m/s = 10/3 m/s
D = (10/3) m/s * 1080 s = 3600 meters