In the classic marriage vow (誓约), couples promise to stay together in sickness and in health. But a new study finds that the risk of divorce among older couples rises when the wife—not the husband—becomes seriously ill.

       “Married women diagnosed with a serious health condition may find themselves struggling with the impact of their disease while also experiencing the stress of divorce,” said researcher Amelia Karraker.

       Karraker and co-author Kenzie Latham analyzed 20 years of data on 2,717 marriages from a study conducted by Indiana University since 1992. At the time of the first interview, at least one of the partners was over the age of 50.

       The researchers examined how the onset (发生) of four serious physical illnesses affected marriages. They found that, overall, 31% of marriages ended in divorce over the period studied. The incidence of new chronic (慢性的) illness onset increased over time as well, with more husbands than wives developing serious health problems.

       “We found that women are doubly vulnerable to marital break-up in the face of illness,” Karraker said. “They’re more likely to be widowed, and if they’re the ones who become ill, they’re more likely to get divorced.”

       While the study didn’t assess why divorce is more likely when wives but not husbands become seriously ill, Karraker offers a few possible reasons. “Gender norms and social expectations about caregiving may make it more difficult for men to provide care to sick spouses,” Karraker said. “And because of the imbalance in marriage markets, especially in older ages, divorced men have more choices among prospective partners than divorced women.”

       Given the increasing concern about health care costs for the aging population, Karraker believes policymakers should be aware of the relationship between disease and risk of divorce.“

       Offering support services to spouses caring for their other halves may reduce marital stress and prevent divorce at older ages,” she said. “But it’s also important to recognize that the pressure to divorce may be health-related and that sick ex-wives may need additional care and services to prevent worsening health and increased health costs.”

解析：A。根据题干中的marriage vows可定位至文章第一段。该段指出在传统的结婚誓言中，夫妻双方承诺无论疾病与健康都会和对方在一起。但一项新的研究发现，当妻子（而不是丈夫）身患重病时，老年夫妇离婚的风险会上升。由此可知，结婚誓言并不能保证婚姻的持久，故正确答案为A。原文没有对比结婚誓言的约束力，故B选项排除。C项利用seriously作干扰，但原文为seriously ill（重病），并非说夫妻双方不再认真对待婚姻，故C项错误。D选项和原文中“老年夫妇离婚风险上升”相悖，故错误。