This example renders a smiley face using React components and SVG primitives, with a yellow circle for the head, two black eyes, and a curved mouth. The mouth is generated with the D3 `arc()` generator, which defines an annular sector path based on inner and outer radii and start/end angles. The face is centered within a 960×500 viewport, and all elements are positioned via a `<g>` transform. The code imports the `arc` function from D3 v7 and uses React 16.9 for component structure, while the SVG is drawn directly in JSX.