Answer: Option B
$$\eqalign{
& {\text{Time taken by train to cross a pole}} \cr
& {\text{ = 9 sec}} \cr
& {\text{Distance covered in crossing a pole}} \cr
& {\text{ = length of train}} \cr
& {\text{Speed of the train}} \cr
& {\text{ = 48 km/h}} \cr
& = \left( {\frac{{48 \times 5}}{{18}}} \right)m/\sec \cr
& = \frac{{40}}{3}m/\sec \cr
& \therefore {\text{Length of the train}} \cr
& {\text{ = Speed }} \times {\text{Time}} \cr
& {\text{ = }}\frac{{40}}{3} \times 9 \cr
& {\text{ = 120 m}} \cr} $$