Final answer:
A scatter plot is a graphical tool used to illustrate the relationship between two variables, such as the cost of operating an airliner and the number of passengers served by the airline.
So option (A) is correct.
Step-by-step explanation:
The graphical tool used to illustrate the relationship between matched observations of two variables, such as the annual cost of operating a commercial airliner (y) and the annual number of passengers served by the airline (x), is a scatter plot. Economic models can be solved algebraically or graphically, with different types of graphs suited for various data representations. The line graph is typically used to show the relationship between two variables, while a pie chart is used to illustrate how a whole is divided into proportional parts, and a bar graph compares values using bars where the length or height of the bars represents the measured value. However, a scatter plot specifically represents individual data points on a two-dimensional plane, showing how one variable is related to another.