A bar chart displays the ten most populous countries in 2020 using React to render SVG elements and D3 utilities for data loading and scales. The code fetches UN population data via `d3.csv`, maps it with a custom row function, and applies `scaleBand` and `scaleLinear` to position and size rectangles. Custom tick lines are generated manually from `xScale.ticks()`, while React’s `useState` and `useEffect` manage the asynchronous loading state.