题目内容：
根据下列材料，请回答题This fall the Pew Research Center，in association with TIME，conducted a nationwide poll exploring the contours of modern marriage and the new American family．And of all the transformations our family structures have undergone in the past 50 years，perhaps the most profound is the marriage differential that has opened between the rich and the poor．In l960 the median household income of married adults was l2％higher than that of single adults，after adjusting for household size．By 2008 this gap had grown to 41％．In other words，the richer and more educated you are，the more likely you are to marry，or to be married-0r， conversely，if you’re married，you’re more likely to be well off．
To begin the question of why the wealth disparity between the married and the unmarried has grown so much，it might be useful to take a look at the brief but illustrative marriage of golfer Greg Norman and tennis star Chris Evert，who married in June 2008 and divorced l5 months later．From all reports，their union had many of the classic hallmarks of modern partnerships．The bride and groom had roughly equal success in their careers．Being wealthy，sporty and blond，they had similar interests．
This is typical of the way many marriages start．Americans are increasingly marrying people who are on the same socioeconomic and educational level．Since more women than men have graduated from college for several decades，it’s more likely than it used to be that a male college graduate will meet，fall in love with，wed and share the salary of a woman with a degree．Women’s advances in education have roughly paralleled the growth of the knowledge economy，so the slice of the family bacon she brings home will be substantial．
On the face of it，this might explain why fewer people are married．They want to finish college first．In 2010 the median age of men getting hitched for the first time is 28．2，and for women it’s 26．1．It’s gone up about a year every decade since the’gos．
But here's the rub．In the past two decades，people with only a high school education started to get married even later than college graduates．In l990 more high-school-educated couples than college graduates had made it to the altar by age 30．By 2007 it was the other way around．What has brought about the switch?It’S not any disparity in desire．According to the Pew survey，46％of college graduates want to get married，and 44％of the less educated do．
Promising publicly to be soreeone’S partner for life used to be something people did to lay the foundation of their independent life．It was the declaration of adulthood．Now it’S more of a finishing touch，the last brick in the edifice，sociologists believe．“Marriage is the capstone for both the college—educated and the less well educated．”says Johns Hopkins’Cherlin．“The college—educated wait until they’re finished with their education and their careers are launched．The less educated wait until they feel comfortable financially．”But that comfort keeps getting more elusive．“The loss of decent—paying jobs that a high—school—educated man or woman could get makes it difficult for them to get and stay married，”says Cherlin．As the knowledge economy has overtaken the manufacturing economy，couples in which both partners’job opportunities are disappearing are doubly disadVantaged．So they wait to get married．
The marriage between Greg Norman and Chris Evert is used to illustrate________． A．the rise of women in socioeconomic status
B．the typical features of modern marriage
C．the example of happy marriage
D．the fragility of modern marriage
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