This example demonstrates a minimal integration of React and D3 in a single-page application. It renders a static "Hello" message inside a React component, with the page styled to have no margins and hidden overflow. The code imports React, ReactDOM, and the `range` function from D3 v6, then mounts the App component to the root div. The HTML loads React 17, ReactDOM 16.7, and D3 6.5 from CDN, relying on a bundled JavaScript file for execution.