A line chart shows the average depression percentage for four income groups, ordered from Low to High, based on a mental health CSV dataset. The SVG rendering uses D3 v7 scales (`d3.scalePoint`, `d3.scaleLinear`) and the `d3.line` generator to draw a steelblue path, with red circles and value labels marking each computed average. The chart is built with D3’s DOM selection and appended to an HTML container, including axis labels and a title.