For decades, materials scientists struggled to explain the extraordinary durability of ancient Roman concrete, which has survived for millennia in harsh marine environments. Traditional volcanic ash-based formulations do not fully account for this longevity. Recently, researchers analyzed mineral phases at the microscopic scale and discovered 'lime clasts'—small, white mineral chunks long dismissed as the result of poor mixing. Instead, these clasts served as a source of calcium that could dissolve and recrystallize, effectively self-healing cracks that developed over time. This finding reveals that the Romans did not merely benefit from high-quality raw materials, but deliberately employed sophisticated chemical engineering techniques to ensure their structures' endurance.
Which choice best describes the function of the underlined sentence in the text as a whole?
- It explains the mechanism by which a previously misunderstood feature of Roman concrete contributes to the material's durability.Answer
- BIt summarizes the passage's primary conclusion regarding the general architectural sophistication of ancient Roman builders.
- CIt contrasts the chemical properties of volcanic ash with those of the newly discovered lime clasts.
- DIt introduces a historical hypothesis to explain why Roman engineers chose to incorporate mineral chunks into their concrete.