人的性别是在父亲的精子与母亲的卵子相遇的那一刻就决定了的。婴儿落地,人们从生殖器的外貌得知他或她的性别,所以,生殖器官是第一性征。除了生殖器官之外,两性间身体上的不同特征是第二性征。人在婴幼儿期,第二性征并不明显,到了青春期,人的第二性征才会逐渐显露出来。也就是说,青春期发育是从第二 The gender of a person is determined at the moment the father’s sperm meets the mother’s egg. When the baby lands, people learn about his or her sex from the appearance of the genitalia. Therefore, the reproductive organs are the first signs. In addition to reproductive organs, the different characteristics of the body between the sexes are secondary sexual characteristics. In infants and young children, the secondary sexual characteristics are not obvious. By the time of adolescence, people’s secondary sexual characteristics will gradually emerge. In other words, adolescent development is from the second