Just east of downtown Irvine, in southern California, a pastoral landscape is under construction. Little by little, a former military airport is being dismantled, to be replaced by grass, trees and a canyon 70 feet (21 meters) deep. When it is finished, Orange County"s Great Park will cover 1,350 acres (550 hectares), more than one-and-a-half times as much as Central Park in New York.Thebiggest landscaped municipal park to be built in more than a century, it reveals much about how American attitudes to open space have changed. Urban parks are back in fashion. In Denver, an 80-acre park opened in September on the site of another disused airport. New York plans to build a huge park on top of the Fresh Kills landfill in Stat-en Island. Innumerable town squares and pocket parks have been created or beautified, even in places like Detroit. City planners, who once viewed parks as financial drains and nests of crime, now see them as magnets for tourists and creative types. The great parks that were built in the second half of the 19th century were intended to counteract the ill effects of city living, and so are the new ones. But the perceived ills have changed. Frederick Olmsted, who designed Central Park and many others, wanted to provide people with a break from their tough, dirty jobs. Ken Smith, the Great Park"s architect, reckons the residents of Orange County are quite idle enough. What they need is exercise: hence the park"s proposed 21 football fields and 12 baseball fields, together with some exhausting-looking walks. Another difference is that parks are now expected to function like natural ecosystems as well as looking like them. The Great Park will use recycled water in its lake (older parks often used mains water). The runways will be dismantled and turned into roads and a memorial In a nod to the local-food movement, the park will include land for farming. Even the car park will be situated in an orange orchard. Most striking of all is the new parks" deference to history. America"s great 19th-century landscape architects saw the land as a blank slate. An entire village was pulled down to build Central Park. By contrast, Denver"s park preserves a control tower, and the Great Park will convert an air-dock into a museum and retain the outline of a runway. A river diverted underground by the marines will be restored to its former course. The preservation lobby is stronger these days. And besides, says Yehudi Gaffen, a partner in the Great Park project, "Southern California has so little history that we should try to keep some of it." According to Paragraph 3, Great Park in Orange County was designed to

A. provide exhausted people with relaxation and happiness.
B. offset the impact of the tough and dirty jobs they keep.
C. give residents the place of doing exercise.
D. attract more tourists and promote the living standards.