This example assembles a smiley face from modular React components, rendering a yellow circle with eyes and an arc-shaped mouth as SVG elements. The mouth uses the `d3.arc()` API to generate a path with specified inner and outer radii and angular extents. Each facial feature is a separate React component (`BackgroundCircle`, `Eyes`, `Mouth`) receiving numeric props like `eyeOffsetX`, `eyeRadius`, and `mouthWidth`. The visualization is computed declaratively in React, with D3 providing only the arc path generation, and the final SVG is drawn at fixed 960×500 pixel dimensions.