This example demonstrates D3 selections on a static HTML page. It shows how `d3.select` targets the first paragraph inside a `#container` div and turns its text red, while `d3.selectAll` applies a larger font size to every paragraph on the page. The code uses the `select` and `selectAll` APIs directly from the D3 v3 module, with the styling applied via `.style()`. No external data is involved; the visualization is purely a styling exercise on pre-existing markup.