A smiling face rendered in SVG animates its eyebrows upward and downward in a looping two-second cycle. The face is constructed entirely through D3.js v5 DOM manipulation, using `select` to target the root `svg` element, then appending and positioning circles for the eyes, rectangles for the eyebrows, and a path built from `arc` for the mouth. The eyebrow animation is driven by chained `transition().duration(2000)` calls that alternately shift the parent group’s `transform` attribute, demonstrating basic tweened state changes on SVG attributes. The composition is centered via a translated group, with hardcoded spacing values for facial features.