This page displays country-level trends in Population, GDP, and Internet Users over time for a selected country (China), shown in two charts. The first is a multi-series line chart, and the second combines bar and line mark types for comparison. Both are rendered as SVG. The example uses d3.tsv to load the data, and defines scales, axes, and marks via the d3.v7 API, including `scaleLinear`, `scaleBand`, `axisBottom`, and `line`. A legend is drawn manually with SVG elements.