This example demonstrates an interactive dropdown menu that lets users select a pollutant metric such as NO2, Ozone, PM2.5, or PM10. When an option is chosen, the selection is logged to the browser console. The interface uses React hooks, specifically `useState`, to manage the selected value, and a reusable `Dropdown` component built with React’s `select` and `option` elements. The code relies on React 16.13.1 and ReactDOM for rendering, with inline CSS for styling the large text and dropdown.