A dropdown menu controls a single line chart that plots baby name popularity over time, showing the annual count for a selected name. The code reads from a CSV file and uses D3 v4 to render an SVG with axes and a smooth animated transition. The user selects a name from the menu to trigger a `transition` that updates the line path, colored via a sequential scale. The display uses `d3.csv` for data loading and `d3.line` for the path generation, with a simple but effective interactive filter.