This line chart compares population distribution across four regional parts for eight major countries, including China, India, and the United States. Data is loaded from a remote TSV file and parsed with `d3.tsv`. The visualization uses `d3.scaleLinear` for axes, `d3.scaleOrdinal` for color mapping, and `d3.group` to organize data by country. Each country’s line is rendered as an SVG path with interactive hover dots that trigger a tooltip, while grid lines and axis labels improve readability.