Final answer:
A line graph is a graphical method that shows the relationship between two variables with one on the horizontal axis and the other on the vertical axis. Pie charts, ogives, crosstabulations, and dot plots serve different purposes and are not specifically designed to show relationships between variables.
Step-by-step explanation:
Among the options provided, a line graph is appropriate to show the relationship between two variables. On a line graph, one variable is plotted on the horizontal axis and the other on the vertical axis, and the points are connected by lines to illustrate how one variable changes in relation to the other.
A pie chart is used to show how a whole is divided into parts, with the size of each 'slice' representing the proportion of each part to the whole. An ogive is a type of line graph that represents cumulative frequency or cumulative percentages. A crosstabulation is a type of table that displays the frequency distribution of variables, but does not graphically represent the variables, unlike the dot plot, which shows each data point individually on the graph as a dot and can be used to see the distribution of a dataset or as a comparison between different groups. However, for showing the relationship between two variables, the line graph specifically is designed to illustrate how one variable changes as the other one does.