Until the 1980s, the American homeless population comprised mainly older males. Today， homelessness strikes much younger part of society. In fact, a 25-city survey by the U. S. Conference of Mayors in 1987 found that families with children make up the fastest growing part of the homeless population. Many homeless children gather in inner cities; this transient(变化无常的) and frequently frightened student population creates additional problems 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 counted as children because they do not stay in family shelters and tend to live by themselves on the streets. Federal law, the Stewart B. McKinney Homeless Assistance Act of 1987, includes a section that addresses the educational needs of homeless children. The educational provisions of the McKinney Act are based on the belief that all homeless children have the right to a free，appropriate education.

1. It is implied in the first paragraph that ____.

A) the writer himself is homeless, even in his eighties

B) many older homeless residents are going on strike in 25 cities

C) there is a serious shortage of academic facilities

D) homeless children are denied the opportunity of receiving free education

2. The National Coalition for the homeless believes that the number of homeless children is _____.

A) 350，000

B) 1，500，000

C) 440，000

D) 110，000

3. One part of the homeless population is difficult to estimate. The reason might well be ____.