This example demonstrates a minimal pattern for combining React and D3.js, where React manages the component lifecycle and D3 performs direct DOM manipulation. The App component renders a single div element, and after the initial mount, the `useEffect` hook triggers a D3 selection. The `select()` function from D3 targets the DOM node referenced by React’s `useRef` hook, and the `.text()` method sets the div’s content to "Hello D3 & React." This shows how D3’s imperative API can be applied to a React-managed element.