This example visualizes the average vehicle fuel efficiency by year using a line chart with red data points and labeled values. The chart is built with D3 v7, loading CSV data from a cars dataset and parsing it with `d3.csvParseRows`. The code groups the data by year and calculates the mean mileage using `d3.rollup` and `d3.mean`, then renders the trend with a line generator and axes. The visualization is rendered as an SVG, showing how average MPG varies across model years.