题目内容：

    According to a new US study, couples who expect their children to look after them in old age should hope they have daughters because daughters are twice as attentive as sons overall.

The research by Angelina Grigoryeva, from 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 old Americans concluded that gender(性别) is one of the most important things that decide whether or not people will actively care for their elderly parents.

In a paper presented at the annual conference of the American Sociological Association in San Francisco, she concludes that simply having a sister makes men 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.

"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 health. The census showed that those who provide 50 hours or more of care a week while trying to hold down a fulltime job are three times more likely to be struggling with ill health than their working counterparts who are not carers.

1.According to the passage, what’s the most important factor to predict if people will actively care    for the elderly?

A.Education. B.Gender. C.Career. D.Income.

2.The US study finds that_____.

A.having a sister makes men less likely to look after their parents

B.sons are twice as likely as daughters to care for parents in old age

C.sons are unwilling to leave caregiving responsibilities to their sisters

D.sons and daughters seem to give equal care to their parents

3.What does the author stress in the last paragraph?

A.People should give up their job to care for the elderly.

B.Many care providers work longer hours than others.

C.Many care providers have potential health problems.

D.People shouldn’t pass on caring responsibilities to others.

4.The author develops the text by _______.

A.explaining social networks of careers B.describing people' s experiences

C.analyzing various researches and data D.comparing different gender