单项选择题

The modern urban planning and redevelopment movement (1) in response to the (2) and dirtiness of the slum areas which were (3) by the Industrial Revolution in the 19th century. Reformation of these areas (4) the objective of early city planners, who imposed regulatory laws establishing (5) for (6) , sanitation, water supply, sewage and public health conditions. Urban planners also introduced parks and playgrounds into crowded city neighborhoods, (7) places for recreation, as well as (8) relief.
The chief new urban-planning concept of the early 20th century was zoning—the regulation of building activity to set (9) of height and (10) and to protect established neighborhoods.
Urban territory (11) as a result of improved public transportation. Workers could live far from their jobs, traveling back and forth by bus, subway, or car.
By the middle of the 20th century, urban planning (12) its focus. Planners realized that factors of city living must be considered as a whole, so they aimed less (13) attacking (14) problems than at the improvement of entire urban surroundings.
Another (15) of urban building has been the building of experimental new towns and cities. In Great Britain, India, Israel, and South America (16) new cities (17) built entirely from plans. Urban planning was an important (15) in Europe after World War Ⅱ, (19) urban planners directed the reconstruction of (20) areas.

15（）

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