Answer:
A) This is an example of a fixed cost because the cost doesn't vary with the number of trains.
Step-by-step explanation:
A fixed cost is a cost that does not vary as the total output varies. In this case, the number of trains using the tracks would be the total output, and the tracks need to bee cleaned regardless of how many trains will use them. Since the costs do not vary depending on the number of trains that will use the tracks, it is considered a fixed cost.