This example demonstrates a simple React application with a pet-selection dropdown, showing how to manage and update state through user interaction. The code uses the `useState` hook to track the selected value and passes it to a custom `Dropdown` component built with React’s `select` and `option` elements. ReactDOM renders the `App` component into the DOM, while the dropdown’s `onChange` event triggers `setSelectedValue` to update state and log the choice to the console. The HTML file loads React and ReactDOM from external production scripts.