A multi-line chart displays PM2.5 air pollution values per year for a selected country, drawn as SVG paths using D3 v5 within a React framework. A dropdown menu lets the viewer choose a country, triggering a redraw of the line chart and its color legend. The visualization uses d3.line, d3.curveBasis, d3.scaleLinear, and d3.scaleOrdinal, with data loaded from a CSV via d3.csv and processed into yearly series.