阅读理解

　　Great changes have been made in family life because of science and industry．

　　In the past, when more Americans lived on farms, the typical family had many children．In a farm family, parents and their children often lived with grandparents．Often too, uncles and aunts lived nearby．But when industry became more important than agriculture(农业)in American life, families became smaller because industry requires workers who are ready and able to move off the land and to move again whenever necessary．And large families cannot be moved from place to place as smaller families can．Therefore, at present people tend(易于)to have smaller families．

　　In the future, because of industrialization(工业化), a typical family will be required to move even more often than now, so families will be even smaller．The typical family may remain childless and consist only of a man and a woman．A small number of families may take raising children as their chief work．At the same time they may also raise other people’s children, leaving those families free to move from job to job．