A yellow smiley face with animated eyebrows demonstrates fundamental D3.js DOM manipulation and transitions. The face is built by appending SVG circles for the eyes and face, rectangles for eyebrows, and a path generated with `d3.arc` for the mouth. Using `.transition().duration(2000)`, the eyebrow group shifts vertically down and back up, creating a repeated motion. The code explicitly imports `select` and `arc` from the D3 v5 library.