TEXT C The greatest impact on the family over the last 50 years has been the changing role of the wife. These changes have affected not only her life but also that of her husband and children. The family has changed from an economically defined unit under the authority of the father and having minimal interpersonal emotional ties to a unit with strong emotional ties directed primarily by the mother to her husband and children. This meant a removal of the woman from the community into the much more private setting of the nuclear family. One important result is greater emotional and general psychological seclusion of the woman, which clearly implied that the female role was culturally a secondary one. In recent decades it has become clear that for a distinct minority of American women the traditional mother role in the seclusion of the home is no longer acceptable. For many the family is of diminishing importance. The development of education for women has been a crucial factor in this change. Today, over 80% of all women complete four years of high school as compared to only 35% in 1940. This is related to the fact that marriage now occurs a year later for the average woman. The proportion of women aged 20 to 24 who are single increased from 28% in 1969 to 40% by the mid 1970s. Childbearing is being postponed so that, compared to the 1960s, 10% fewer women bear their first child in the two years immediately following marriage. Furthermore, more women today remain childless. Work, older age at marriage, and fewer children are the basic changes that have taken place in women’s roles in recent years. The trend among women is toward increased education, and this is linked to other role changes. The higher a woman’s educational attainment, the more likely she is to work, to stay in the labour force longer, and to have more job opportunities available to her. This further suggests that when women are married their work has a great impact on their marriage. For example, since working wives contribute 25% to 40% of their total family income, their position as decision-makers in the family is usually strengthened. A sociologist points out that the social trends towards increased education for women not only mean more work experience but also delayed marriage and decreased fertility. These changes, in turn, point the way toward even greater labour force participation throughout the life cycle. The number of women entering the work force is rapidly increasing. Women outnumber men in the total population by about 7 million. When that is added to the fact that labour force participation of males is slowly declining because of the trend toward earlier retirement, "it may not be too long before one out every two American workers is a woman." What is the direct cause of the improvement of women’s position in the family

A. Her education attainment.
B. Her increased income.
C. Her work experience.
D. Her increased job Opportunities.