On a recent visit to Europe, your friend Ryan admired the famous Roman aqueducts that were used to carry water to their towns. They were built using structures that spanned spaces and were able to support the weight above those spaces. Ancient Romans used bricks and other materials to create these structures. What is type of structure Ryan observed that is so crucial to the construction of these aqueducts? (1 point)
domes
barrel vaults
flying buttresses
arches