Until the 1980s, the American homeless population (47)______ mainly older males. Today, homelessness strikes much younger part of society. In fact, a 25-city (48)______ by the U.S. Conference of Mayors in 1987 found that families with children make up the fastest growing part of the homeless (49)______. Many homeless children gather in inner cities; this transient (变化无常的) and frequently frightened student population creates (50)______ problems — both legal and educational — for already overburdened school administrators and teachers. Estimates of the number of homeless Americans (51)______ from 350,000 to three million. Likewise, estimates of the number of homeless school children (52)______ radically. A U.S. Department of Education report, based on state estimates, states that there are 220, 000 homeless school-age children, about a third of whom do not (53)______ school on a regular (54)______. But the National Coalition for the Homeless estimates that there are at least two times as many homeless children, and that less than half of them attend school regularly. One part of the homeless population that is particularly difficult to count consists of the "throwaway" youths who have been cast of their homes. The Elementary School Center in New York City estimates that there are 1.5 million of them, many of whom are not (55)______ as children because they do not stay in family (56)______ and tend to live by themselves on the streets. Word Bank A) basis B) experiment C) population D) drop out E) comprised F) range G) attitude H) vary I) attend J) counted K) recent L) survey M) shelters N) potential O) additional