This example demonstrates a pet-selection interface built with React and D3. It displays a dropdown menu that lets users choose from six pet options, with the selected value managed through React’s `useState` hook. The UI uses a reusable `Dropdown` component that maps over option objects and triggers state updates via an `onSelectedValueChange` callback. The page loads D3 v7, React 16.9, and ReactDOM from CDNs, while the app logic in `index.js` renders the component hierarchy into a root element.