A smiling face is rendered as a static SVG composed of modular React components: a yellow background circle, two eyes, and a mouth. The mouth is drawn using the D3 `arc` generator with fixed start and end angles. The code splits each facial feature into separate ES6 modules (`BackgroundCircle.js`, `Eyes.js`, `Mouth.js`) that are imported into the main `index.js` file, which uses ReactDOM to render the nested SVG elements inside a `<g>` transform.