补全短文
in family shelters on a regular basis cast off less than A. who have been 【T13】______their homes B. a third of whom do not attend school 【T14】______ C. that 【T15】______half of them attend school regularly D. because they do not stay 【T16】______ Estimates of the number of homeless Americans range from 350,000 to three million. Likewise, estimates of the number of homeless school children vary radically. A U. S. Department of Education report, based on state estimates, states that there are 220, 000 homeless school-age children, about 【T17】______. But the National Coalition for the Homeless estimates that there are at least two times as many homeless children, and【T18】______ . One part of the homeless population that is particularly difficult to count consists of the " throwaway" youths 【T19】______. The Elementary School Center in New York City estimates that there are 1. 5 million of them, many of whom are not counted as children 【T20】______and tend to live by themselves on the streets.