Which type of chart is not suitable for depicting relationships over time?

The pie chart is not suitable for depicting relationships over time because it is designed to represent static data at a single point in time, illustrating the proportions of a whole by showing how various parts contribute to that whole. Pie charts are effective for visualizing categorical data and comparing parts of a dataset but do not provide a clear view of trends or changes over time.

In contrast, a bar chart, area graph, and line chart are specifically intended to display relationships over time, making it easy to observe trends, fluctuations, and comparisons across different time periods. Bar charts can show changes between distinct time intervals, area graphs emphasize volumes over time, and line charts excel at demonstrating continuous data and connections between values across time. Each of these chart types captures the dynamic nature of time-related information, unlike the pie chart.