This example shows a React-controlled dropdown menu for selecting a pet, with the chosen value displayed in a large label. It demonstrates how React state manages the selected option and passes it to a reusable Dropdown component. The code uses React’s `useState` hook and `ReactDOM.render` to mount the app, while D3 v7 is loaded but not directly used in the rendering logic. The dropdown options are hardcoded in `index.js`, and the interface is styled with plain CSS in `index.html`.