This example demonstrates a pet-selection dropdown menu built with React and D3. It shows a styled `<select>` element populated with pet options, where the currently chosen value is tracked and displayed via React state. The implementation uses React’s `useState` and the custom `Dropdown` component, embedded in a simple app rendered with `ReactDOM`. D3 version 5 and React 16.9 are loaded via CDN, while the UI is styled through CSS, highlighting the integration of React for interactivity and D3 for visualization support.