单选题
Over half the world's people now live in cities. The latest
"Global Report on Human Settlements" says a significant change took place last
year. The report {{U}} {{U}} 1 {{/U}} {{/U}}this week from U.N.
Habitat, a United Nations agency. A century ago, {{U}}
{{U}} 2 {{/U}} {{/U}}than five percent of all people lived in
cities. {{U}} {{U}} 3 {{/U}} {{/U}}the middle of this century it
could be seventy percent, or {{U}} {{U}} 4 {{/U}} {{/U}}six and
a half billion people. Already three-fourths of people in
{{U}} {{U}} 5 {{/U}} {{/U}}countries live in cities. Now most
urban population {{U}} {{U}} 6 {{/U}} {{/U}}is in the developing
world. Urbanization can {{U}} {{U}} 7 {{/U}}
{{/U}}to social and economic progress, but also put {{U}} {{U}} 8
{{/U}} {{/U}}on cities to provide housing and {{U}} {{U}} 9
{{/U}} {{/U}}. The new report says almost two hundred thousand people move
{{U}} {{U}} 10 {{/U}} {{/U}}cities and towns each day. It says
worsening inequalities, {{U}} {{U}} 11 {{/U}} {{/U}}by social
divisions and differences in {{U}} {{U}} 12 {{/U}} {{/U}}, could
result in violence and crime {{U}} {{U}} 13 {{/U}} {{/U}}cities
plan better. Another issue is urban sprawl (无序扩展的城区). This is
where cities {{U}} {{U}} 14 {{/U}} {{/U}}quickly into rural
areas, sometimes {{U}} {{U}} 15 {{/U}} {{/U}}a much faster rate
than urban population growth. Sprawl is {{U}} {{U}}
16 {{/U}} {{/U}}in the United States. Americans move a lot. In a recent
study, Art Hall at the University of Kansas found that people are moving away
from the {{U}} {{U}} 17 {{/U}} {{/U}}cities to smaller ones. He
sees a {{U}} {{U}} 18 {{/U}} {{/U}}toward "de-urbanization"
across the nation. {{U}} {{U}} 19 {{/U}} {{/U}}urban economies
still provide many {{U}} {{U}} 20 {{/U}} {{/U}}that rural areas
do not.