【正确答案】 B

【答案解析】[听力原文] In 1858, a British scientist named William Farr set out to study the 'marital condition' of the people of France. He divided the adults into three categories: the 'married,' consisting of husbands and wives; the 'unmarried,' defined as the bachelors and spinsters who had never married; and finally the 'widowed,' those who had experienced the death of a spouse. Using birth, death and marriage records, Farr analyzed the death rates of these three groups at various ages. The work, a groundbreaking study that helped establish the field of medical statistics, showed that much more unmarried people died from disease than the married. And the widowed, Farr found, lived worst of all. Farr was among the first scholars suggesting that there is a health advantage to marriage. Married people, the data seemed to show, lived longer and healthier lives. 'Marriage is a healthy estate,' Farr concluded. 'The single individual is more likely to be wrecked on his voyage than the lives joined together in marriage.' While Fart's own study is no longer relevant to the social realities of today's world because his three categories don't include couples living together, gay couples and the divorced, for instance, his finding about the health benefits of marriage seems to have stood the test of time. Although better health among the married sometimes simply reflects the fact that healthy people are more likely to get married in the first place, scientists have continued to prove the 'marriage advantage': The fact that married people, on average, appear to be healthier and live longer than unmarried people. What did William Farr study by dividing the adults into three types at various ages?