Part 4A (第4問A)

Towering skyscrapers are a symbol of modern society. In the late 1800s, new technological developments made very tall buildings possible. One development was steel building technology. Before that, architects were required to create thicker stone walls to support taller building. These walls were extremely heavy and allowed less room for windows and light. After mass production of steel was introduced, architects began to use steel frames to support a building’s weight. Steel was much lighter and stronger than stone, while taking up much less space. At the same time, elevator technology and fire-resistant building materials also helped make skyscrapers possible.