Will America’s cities ever again be places most people want to live in It seems unlikely. hereas in 1970 America’s suburbs contained 25% more families than its cities, today they contain 75 % more. Middle-class families -- "the bedrock of a stable community", in the words of the Department of Housing and Urban Development -- associate cities with poverty and therefore crime. 41)______ . No wonder so many families equate the American dream with a home in the suburbs.But the resulting urban sprawl carries a cost. A report this week from the Sierra Club, which has been preaching ecological sensitivity for more than a century, underlines what it calls "the dark side of the American dream" ~ traffic congestion; commuting journeys that "steal time from family and work "; air and water pollution; lost farfnland and recreational space; increased flooding; and more taxes to pay for a suburban infrastructure that ranges from policing to sewage systems. 42)______Putting numbers to its argument, the Sierra Club reckons air pollution "costs US agriculturemore than ＄ 2.5 billion every year," and it argues that the paving over of natural wetlands helps produce the floods that cost America an average of $ 4.3 billion a year. In the period from 1970 to 1990, urban sprawl led the twin cities of Minneapolis -- St Paul, in Minnesota, to close 162 schools in and around the city centers while building 78 new ones in the outer ’suburbs. Between1970 and 1995, Maine spent 6ver ＄ 338 million building new schools even as the number of students in its public schools fell by 27,000. 43)______44)______ Among the country’s largest cities, the most threatened, apparently, are the citizens of Atlanta; among medium-sized cities, it is the people of Orlando, Florida, who have most to fear; and among small cities, the inhabitants of McAllen, Texas. As for Los Angles, the "grand-daddy of sprawl", the city deserves a “dishonorable mention”, along with San Diego and Phoenix.45 )______ One idea being tried in parts of Michigan and Maryland ’is for communities to buy farmland or environmentally sensitive land to prevent its development; another idea, practiced in Oregon and Washington state, is to set an "urban growth boundary" to enclose an urban area within an inviolate green belt; a third is to offer tax inducements to communities that forgo development rights. But in the land of the car, perhaps the most unlikely idea is that Americans will follow the example of New Jersey, which recently voted for higher petrol taxes to preserve a million acres of undeveloped land over the next ten years.A. Moreover, as the suburb expands, the inner city’s tax base shrinks, setting off a viciouscycle of higher taxes, lower corporate profits, higher joblessness and lower property values.B. It was obvious that after 1970 people preferred to live in the suburb while work in the city.C. Can urban sprawl be repulsedD. They have a point: the poverty rate in America’s urban areas rose from 14.2% in 1970 to 21.5% in 1993, with most of the increase in the inner-city areas from which the middle class has fled.E. Meanwhile, the exhaustion of commuters is hardly lessened by new and better roads, since each 1% increase in new lane-miles generates within five years a 0.9% increase in traffic.F. The house in the suburb may not be full of conveniences of every sort, so cars are the only means for shopping and transportation.G. All this, the Sierra Club maintains, illustrates the threat that urban sprawl represents to the quality of life. 44（）