Roman arches may develop into ___________.

• A. Dome
• B. Barrel vault
• C. Parallel vault
• D. Groin vault

Answer: (D)

The idea here is how an arch can be extended into a three‑dimensional space to create a vault. A barrel vault comes from taking a single arch and extending it along a line, producing a tunnel‑like ceiling. When two such barrel vaults intersect at right angles, their curved surfaces meet and form a groin vault. The intersecting lines where the vaults cross are the groins, and this arrangement distributes weight more efficiently, allowing larger rooms with thinner walls—something Roman builders mastered. A dome, by contrast, is formed by rotating an arch around a central vertical axis to enclose space, which is a different transformation from extending arches along two directions. So the Roman arch may develop into a groin vault.