This example demonstrates the simplest possible D3 program: it displays the text “Hello D3 version 7” centered on a blank page. The code uses the D3 v7 `select` method to target the `body` element and chain the `.text()` method to set its content. The `index.html` file loads D3 from unpkg, imports the JavaScript bundle, and uses CSS to enlarge the text to 13em for a bold visual effect.