The spatial distribution of different racial and ethnic populations
demonstrates that segregation persists in virtually all of America's housing
markets, from large urban areas to rural counties. What exactly are the ill-
effects of this demographic isolation？ The most extreme geographic segregation
(5) is unique to black Americans and apparently unrelated to economic status and
not explained by preferences for the residence, thus strongly suggesting the
persistence of racial discrimination. In contrast to poor whites, who typically
live dispersed among better-off families, poor blacks, because of residential
segregation, are concentrated in poor neighborhoods. As a result, residential
(10) segregation contributes to the problems of these areas, including high
concentrations of poverty, educational failure, unemployment, extramarital
parenthood, crime, and high mortality. In addition, the increasing importance
of suburbs as centers for commerce and habitation has drained resources from
inner cities and led to a cyclic decline in the political will to address poverty and
(15) urban decline, both of which disproportionately affect ethnic minorities.
In the passage, the author is primarily concerned with

A. hypothesizing about a set of circumstances
B. chronicling the emergence of a phenomenon
C. comparing two conflicting points of view
D. cataloging the cause and effects of a phenomenon
E. arguing the necessity of solving a problem