A dropdown menu lets users select among three options, while a scatterplot displays the relationship between horsepower and weight for cars from the auto-mpg dataset. The visualization uses D3 v5’s `scaleLinear` and `extent` for axes, `axisBottom` and `axisLeft` for ticks, and SVG circles with opacity for data points. Data is loaded via `csv`, and the menu is generated with a reusable `dropDownMenu` function.