The above regression analysis has "number of cars" as the x variable and "fuel consumption" as the y variable. Why does this make more sense than having "fuel consumption" as the x variable and "number of cars" as the y variable? Because we would expect that adding more railcars to a train would cause it to consume more fuel. Because we would like to predict how much fuel a train will consume based on the number of railcars it has attached to it. The first two choices aren't both correct. It doesn't make more sense, it would make more sense to have "fuel consumption" as the x variable and "number of cars" as the y variable. It doesn't make more sense, it would be reasonable to choose either variable to be x