A bar chart displays average body mass index (BMI) by age, using orange rectangles to represent binned age groups. The visualization calculates BMI from weight and height data and aggregates it per age bin. Built with D3 v7, the code uses `scaleLinear`, `axisBottom`, `axisLeft`, and `bin` to construct the axes and data groups. The SVG output is rendered via the `select` and `append` API, drawing axes with tick marks and labeled "Average Body Mass Index" and "Age". Data is loaded from a CSV source.