A dropdown menu built with React selects a pet from a list of five options, displaying the chosen value via the `useState` hook. The `Dropdown` component renders a native `<select>` element, mapping each option to an `<option>` tag and triggering `onSelectedValueChange` on change. Label and select styling come from inline CSS in `index.html`, while `ReactDOM.render` mounts the `App` component to the `#root` element.