Digital SAT Reading and Writing Practice Question #1672

While researching ancient Roman architecture, a student took the following notes: - The Roman Pantheon, completed under Emperor Hadrian in 126 CE, features the world's largest unreinforced concrete dome. - The dome spans 43.3 meters (142 feet) in diameter and height. - Roman engineers used pozzolana, a reactive volcanic ash from Pozzuoli, which formed durable calcium-silicate-hydrate cement. - To reduce the dome's structural weight, engineers used progressively lighter aggregates, switching from dense basalt at the base to lightweight pumice near the top oculus. - The dome has remained structurally intact without steel reinforcement for nearly two thousand years. The student wants to highlight the engineering innovation that allowed the dome to support its own immense weight without collapsing. Which choice most effectively accomplishes this goal?