1-C. I want to be an architect someday, so it'd be great to go sightseeing in cities like Rome, Venice, and Florence.I want to be an architect someday, so it'd be great to go sightseeing in cities like Rome, Venice, and Florence.
2-C. After mass production of steel was introduced, architects began to use steel frames to support a building's weight.After mass production of steel was introduced, architects began to use steel frames to support a building's weight.
3-C. Before that, architects were required to create thicker stone walls to support taller buildings.Before that, architects were required to create thicker stone walls to support taller buildings.