18. - 20. soruları aşağıdaki parçaya göre cevaplayınız.
Under the Roman Republic, brickmaking, particularly in the region of Rome itself, became a major industry, and finally, under the Empire, it became a state monopoly. Brick construction was cheaper than stone due to the economies of scale in mass production and the lower level of skill needed to put it in place. The brick arch was adopted to span openings in walls. Mortar had traditionally been composed of sand, lime, and water, but beginning in the 2nd century BCE, a new ingredient was introduced. The Romans called it pulvis puteoli after the town of Puteoli (modern Pozzuoli), near Naples, where it was first found. The material, formed in Mount Vesuvius and mined on its slopes, is now called pozzolana. When mixed with lime, pozzolana forms a natural cement that is much stronger and more weather-resistant than lime mortar alone, and that will harden even underwater. Pozzolanic mortars were so strong and cheap, and could be placed by labourers of such low skill, that the Romans began to substitute them for traditional mortars inside walls. The concrete made from pozzolana made it possible to create curved shapes and led to the creation of a series of remarkable interior spaces spanned by domes and columns.
18) Which of the following was one of the advantages of brick over stone?