Science makes possible the use of new materials and new methods of producing objects. For example, some 20th-century chairs are made of steel and plastic. These materials, 24 , were undreamed of in the 18th century.
As new materials develop, one invention often 25 another. Steel, for instance, was developed by engineers in the 19th century. 26 its strength, steel soon became a useful building material. 27 steel construction, buildings could then have a great many stories. But no one could be expected to walk up 8, 10, or 30 flights of 28 . Therefore, to make tall buildings more accessible to their users, the elevator 29 . By providing much-needed space in a world 30 people, tall buildings have solved a great problem of the city and have completely changed our way of life.
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