City life is not always a bad thing,but many experts worry a

City life is not always a bad thing,but many experts worry about this __1__.A new report from the Worldwatch Institute says it is having a __2__and the quality of the environment.The environmental research group in Washington released its two thousand seven "State of the World" report last week.Of the three billion people who live in cities now,the report says,about one billion live in __3__.These are areas of poverty,slums that generally __4__like clean water,or even__5__.怎么样填空