Answer: The correct option is (B)

Step-by-step explanation: Let, 'x' be the number of hours for which the bicycle is rented except the first hour.
Then, according to the given information, the cost of renting 1 bicycle is given by

There is a discount of 20% on additional hours 'x' when three or more bikes are rented together.
Since Marty and his family rent four bicycles, so the discount on additional hours for 1 bicycle is given by

Therefore, the total cost of renting 4 bicycles is given by

Thus, the required expression for the cost is

Option (B) is correct.