A smiling face built from basic SVG shapes shows how D3.js v5 can assemble a figure from primitives. The code uses `d3.select` to append a yellow circle for the head, black circles for eyes, and a mouth drawn with the `d3.arc` path generator using specified inner and outer radii plus start and end angles. Positioning relies on the SVG width and height attributes read from the DOM, with the mouth placed inside a transformed `<g>` group. The example demonstrates simple attribute chaining and coordinate math for a playful default output.