Answer: The situation that is most likely to have a constant rate of change is option B: "The total amount paid for gas compared with the number of gallons purchased."
This is because the price of gas per gallon is usually constant, so the rate of change of the total amount paid for gas should be constant with respect to the number of gallons purchased. In other words, if you plot the total amount paid for gas against the number of gallons purchased, you would expect a straight line with a constant slope.
In contrast, the number of flowers in a flower bed compared with the area planted (option A), the distance a delivery truck travels compared with the number of deliveries made (option C), and points scored in a basketball game compared with the number of quarters played (option D) are less likely to have a constant rate of change because they can be affected by various factors such as weather, traffic, player performance, and so on.