1.D before 4 out of every 100 now 10 out of every 100
2.C
3.A one in which people have a quite different idea of what kind of behavior is suitable at various ages,是这句的one吗?
4.B
5.A 从 It doesn't surprise us to hear of a 29-year-old university president or a 35-year-old grandmother,or a 70-year-old man who has become a father for the first time.可推断