(C) 5 : 8
From the question it is given that,
Bus travels 160 km in 4 hours
Train travels 320 km in 5 hours
So, Bus travels a distance in one hour = 160/4 = 40 km/h
Train travels a distance in one hour = 320/5 = 64 km/h
Then the ratio of the distances travelled by them in one hour is = 40/64
Divide both numerator and denominator by 8.
= 5/8
Therefore, the ratio of the distances travelled by them in one hour is 5: 8.