填空题

Half a century ago, most people lived in (36) areas. However, according to the most recent estimate (37) by the United Nations, more than half of all people will live in cities by 2012, for the first time in history. City life is not always a bad thing, but many experts worry about this process of (38) . According to a new report from the Worldwatch Institute, an environmental research group in Washington, it is having a huge (39) on human health and the (40) of the environment. Of the three billion people who live in cities now, about one billion live in (41) settlements. These are areas of poverty, slums, that generally lack basic services like clean water, or even (42) housing. More than 60 million people are added to cities and their (43) areas each year, mostly in slums in developing countries. Molly O’Meara Sheehan, the leading researcher of the Worldwatch report, believes that (44) Policymakers, she says, need to increase investments in education, health care and other areas.
(45) . For example, Freetown in Sierra Leone has established farming within the city limits to meet much of its growing food demands. In Bogota, the capital of Colombia, (46) .