According to a new US study, couples who expect their children to help care for them in old age should hope they have daughters because they are likely to be twice as attentive overall. The research by Angelina Grigoryeva, a sociologist at Princeton University, found that, while women provide as much care for their elderly parents as they can manage, men do as little as they can get away with and often leave it to female family members. Her analysis of the family networks of 26,000 older Americans concluded that gender is the most important predictor of whether or not people will actively care for elderly parents. In a paper being presented at the annual conference of the American Sociological Association in San Francisco, she concludes that simply having a sister makes men statistically likely provide less care. Using data from the University of Michigan Health and Retirement Study, a study which has been tracking a cross-section of over-50s for the last decade, she calculated that women provide an average of 12.3 hours a month of care for elderly parents while men offer only 5.6 hours. "Whereas the amount of elderly parent care daughters provide is associated with limitations they face, such as employment or childcare, sons'caregiving is associated only with the presence or absence of other helpers, such as sisters or a parent's spouse ," she explained. "Sons reduce their relative caregiving efforts when they have a sister, while daughters increase theirs when they have a brother." "This suggests that sons pass on parent caregiving responsibilities to their sisters." In the UK, the 2011 census showed that there are now around 6.5 million people with caring responsibilities - a figure which has risen by a tenth in a decade. But many are doing so at the risk of their own health. The census showed that those who provide 50 hours or more of care a week while trying to hold down a full- time job are three times more likely to be struggling with ill health than their working counterparts who are not carers. The author develops the text by _ . A) explaining social networks of careers B) describing people's experiences C) analyzing various research and data D) comparing different gender behavior
C