Correct option is B
Upstream speed of the boat = 75/5=15 km/hr
Speed of stream = 18 – 15 = 3 km/hr
Downstream speed of the boat = 18+3 = 21 km/hr
Total distance covered by the boat in 4 hours downstream = 4×21 = 84 km
Required difference = 194 – 84 = 110 km