The United States has historically had hig

题目：

The United States has historically had higher rates of marriage than those of other industrialized countries. The current annual marriage (51) in the United States—about 9 new marriages for every 1,000 people—is (52) higher than it is in other industrialized countries. However, marriage is (53) as widespread as it was several decades ago. (54) of American adults who are married (55) from 72 percent in 1970 to 60 percent in 2002. This does not mean that large numbers of people will remain unmarried (56) their lives. Throughout the 20th century, about 90 percent of Americans married at some (57) in their lives. Experts (58) that about the same proportion of today’s young adults will eventually marry.

The timing of marriage has varied (59) over the past century. In 1995 the average age of women in the United States at the time of their first marriage was 25. The average age of men was about 27. Men and women in the United States marry for the first time at an average of five years later than people did in the 1950s. (60) , young adults of the 1950s married younger than did any previous generation in U. S. history.

54().

A.Aproportion 

B.Theproportion 

C.Thenumber 

D.Anumber