Question: You have data for many years on the average price of a barrel of oil and the average retail price of a gallon of unleaded regular gasoline. If you want to see how well the price of oil predicts the price of gas, then you should make a scatterplot with ______ as the explanatory variable.
(a) the price of oil
(b) the price of gas
(c) the year
(d) either oil price or gas price
(e) time