10. According to paragraph 4, who benefited from solving problems associated with skyscraper construction? A . The inventor of the elevator, Elisha Graves Otis B. Engineers and construction workers C. People who used the lower floors of tall buildings D. Real estate developers 11. In paragraph 4, the author provides information about the melting point of metal in order to A . explain why fire safety was a crucial issue for steel-frame buildings B. describe the process by which steel is molded into beams C. argue that there is no way to make steel buildings safe D. support the position that steel was not a good material for use in tall buildings 12. According to paragraph 4, why were terra-cotta tiles used in buildings with steel beams? A. Terra-cotta is lighter than steel.
B. Terra-cotta is a fire-retardant material. C. Terra-cotta tiles were as cheap as bricks. D. Terra-cotta tiles could be used for flooring.
13. Look at the letters that indicate where the following sentence could be added to the passage. Even the air space within the tiles served to insulate the metal from the heat of fire . Where would the sentence best fit?
From the standpoint of real estate developers, the purpose of skyscrapers was to increase rental space in valuable urban locations. But to create usable high-rise buildings, a number of technical challenges needed to be solved . One problem was getting people to the upper floors, since after five or six stories it becomes exhausting to climb stairs. Updated and electrified versions of the freight elevator that had been introduced by Elish Graves Otis in 1853 □ several decades before skyscraper construction □□ solved this problem. Another issue was fire safety. The metal supporting buildings became soft when exposed to fire and collapsed relatively quickly. □ They could melt at 2,700 Fahrenheit, whereas major fires achieve temperatures of 3,000 degrees □ . However, when the metal is encased in fire-retardant materials, its vulnerability to fire is much decreased . [A] In Chicago, a system was developed for surrounding the metal components with hollow tiles made from brick-like terra-cotta . [B ] Such tiles are impervious to fire . [C] The terra-cotta tiles were used both to encase the supporting members and as flooring. [D] A structure built with steel beams protected by terra-cotta tiles was still three times lighter than a comparably sized building that used masonry construction, so the weight of the tiles was not a problem.
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