This example presents two interactive charts built with D3 v7: a multi-series line chart tracking three quantitative variables over time, and a combined bar-and-line chart. The line chart uses `d3.line` to plot valueA, valueB, and valueC against year, while the bar chart draws valueA as rectangles via `d3.scaleBand` and overlays valueB as a line with a secondary `d3.scaleLinear`. Data is loaded asynchronously from a CSV file using `d3.csv`. The code also demonstrates axes, legends, and chart titles.