Which feature allows users to visualize data trends over time in a spreadsheet?

The feature that allows users to visualize data trends over time in a spreadsheet is the chart. Charts are designed to represent data graphically, making it easier to identify patterns, trends, and outliers at a glance. By plotting data points on axes, charts can illustrate how values change over a specified period, providing a visual context that helps users comprehend longitudinal data effectively.

While other options like data tables organize information effectively, they do not provide a visual representation and thus are less suitable for observing trends. Similarly, pivot tables are powerful tools for summarizing and analyzing data but are primarily used for data manipulation rather than visualization. Formulas are essential for performing calculations but do not inherently provide a visual output. Therefore, the best choice for visualizing data trends over time is a chart.