请阅读Passage 2，完成此题。
Passage 2
Until a decade or two ago, the centers of many Western cities were emptying while their edges were spreading. This was not for the reasons normally cited. Neither the car nor the motorway caused suburban sprawl, although they sped it up: cities were spreading before either came along.
Nor was the flight to the suburbs caused by racism. Whites fled inner-city neighborhoods that were becoming black, but they also fled ones that were not. Planning and zoning rules encouraged sprawl, as did tax breaks for home ownership--but cities spread regardless of these. The real cause was mass affluence. As people grew richer, they demanded more privacy and space. Only a few could afford that in city centers; the rest moved out.
The same process is now occurring in the developing world, but much more quickly. The pop-ulation density of metropolitan Beijing has collapsed since 1970, falling from 425 people per hectare to 65. Indian cities are following; Brazil's are ahead. And suburbanization has a long way to run. Beijing is now about as crowded as metropolitan Chicago was at its most closely packed, in the 1920s. Since then Chicago's density has fallen by almost three-quarters.
This is welcome. Romantic notions of sociable, high-density living--notions pushed, for the most part, by people who themselves occupy rather spacious residences--ignore the squalor and lack of privacy to be found in Kinshasa, Mumbai or the other crowded cities of the poor world.
Many of them are far too dense for dignified living, and need to spread out.
The Western suburbs to which so many aspire are healthier than their detractors say. The modern Stepfords are no longer white monocultures, but that is progress. For every Ferguson there are many American suburbs that have quietly become black, Hispanic or Asian, or a blend of every-one. Picaresque accounts of decay overlook the fact that America's suburbs are half as criminal and a
A.Parking spaces
B.Green belts
C.Distant commuters
D.Property developers