Using React hooks and D3 v5, this chart displays the top 10 most populous countries for 2020 from United Nations World Population Prospects 2019 data, loaded via `d3.csv`. It renders SVG rectangles scaled by `d3.scaleLinear` for population and positioned with `d3.scaleBand` for country names, with no axes or labels. The chart updates asynchronously with `useState` and `useEffect`, and `ReactDOM.render` mounts the component.