资料题：Often children have to work because（　）。

In the latter part of the 20th century, child labor remains a serious problem in many parts ofthe world.Studies carried out in 1979, the International Year of the Child, show that more than50 million children below the age of 15 were working in various jobs often under dangerous conditions.Many of these children live in underdeveloped countries in Latin America, Africa, and Asia.Their living conditions are poor and their chances for education minimal.The small income hey bring in, however, is necessary for the survival of the families.Frequently, these families lack the basic necessities af life adequate food, decent clothing and shelter, and even water for bathing.In some countries industrialization has created working conditions for children that are comparable to the wort features of the 19th-centuny factories and mines.In India, for example, some 20,000 children work 16-hour days in match factories.Child-labor problems are not, of course, limited to developing nations.They occur wherever poverty exists in Europe and the United States.The most important efforts to get rid of child-labor abuses (滥用) throughout the world come fro the International Labor Organization (ILO), founded in 1919 and now a special agency of the United Nations.The organization has introduced several child-labor regulations among its members, including a minimum age of 16 years for admission to all work, a higher minimum age for specific types of employment, necessary medical examinations, and regulation of night work.The Lo, however, does not have the power to enforce these regulations it depends on voluntary obedience(服从) of member nations.