Three dropdown menus let a user independently select values for X, Y, and Color from a fixed set of car brands. The example shows how to generate multiple synchronized `<select>` elements with D3’s selection and join operations, using `d3.select` and `.join` to manage the menu lifecycle. As the user changes an option, a text message updates to reflect the current combination of chosen attributes, demonstrating a reusable `menu` function that binds each dropdown to a separate field in the shared state object.