This bar chart displays the pupil-teacher ratio in secondary education for each country in 2015, sourced from UNESCO data. The visualization uses D3.js to create the SVG graphic, sorting countries by ratio and rendering them as horizontal bars. Specific D3 APIs include `csv` for data loading, `scaleBand` and `scaleLinear` for axes, `axisLeft` and `axisBottom` for chart scaling, with the final rendering handled via SVG `rect` elements.