题目内容：
B Having a husband means an extra seven hours of housework each week for women, according to a new study. For men, getting married saves an hour of housework a week. “It’s a well-known pattern,” said lead researcher Frank Stafford at University of Michigan’s Institute for Social Research. “Men usually work more outside the home, while women take on more of the housework.”
He points out that differences among households（家庭）exist. But in general, marriage means more housework for women and less for men. “And the situation gets worse for women when they have children,” Stafford said．
Overall, times are changing in the American home. In 1976, women busied themselves with 26 weekly hours of sweeping-and-dusting work, compared with 17 hours in 2005. Men are taking on more housework, more than doubling their housework hours from six in 1976 to 13 in 2005.
Single women in their 20s and 30s did the least housework, about 12 weekly hours, while married women in their 60s and 70s did the most-about 21 hours a week.
Men showed a somewhat different pattern, with older men picking up the broom more often than younger men. Single men worked the hardest around the house, more than that of all other age groups of married men.
Having children increases housework even further. With more than three children, for example, wives took on more of the extra work, clocking about 28 hours a week compared with husbands’10 hours.According to the “well-known pattern” in Paragraph 1, a married man___________. A．takes on heavier work
B．does more housework
C．is the main breadwinner
D．is the master of the house
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