This example demonstrates a minimal integration of React with D3, rendering a simple `<div>` with the text “hi”. The code imports React and ReactDOM to mount the `App` component into the DOM’s `#root` element, while also importing the `arc` function from d3 to show how D3 modules can be included. The page loads React 16.9, ReactDOM, and D3 v6 via CDN, with CSS setting the body margin to zero and hiding overflow. It serves as a starter template for combining React’s declarative UI with D3’s visualization utilities.