有些呼叫已完成通信而结束，有些呼叫则因种种原因不能达到通话目的，最终离开系统。归纳起来，一个呼叫会遇到几种最基本的情况。
参考答案：
①主叫用户与被叫用户接通，实现通话；
②被叫用户忙，未能接通；
③被叫用户久不应答，未能通话；
④主叫用户由于各种原因（如拨错号码）中途挂机，未能通话；
⑤由于电话交换机设备忙，不能与被叫用户进行通话，造成呼损。
| The first and most important agents of socialization are the people who care for infants. In the earliest months, messages from nurturers constitute the child’s basic understanding of the world around it. This is the infant’s first introduction to the language that shapes perception and elicits emotion. Another powerful source of information and socialization is the friendship of peers. Peers are equals that one can deal with on the same level as oneself, whereas parents are superiors. The heavy emotional overlay of family relationships makes some kinds of learning difficult. Much formal socialization is placed in the hands of professionals. Teachers from kindergarten on are specifically designated agents of socialization. Ideally, a teacher is one who has both knowledge and the skills to present it. During the course of teaching their subjects, classroom instructors provide role models and attempt to convey the excitement of learning itself. In earlier times, parents, friends and teachers would comprise the list of primary childhood socializers. Children’s books, comics and magazines might also have been mentioned as sources of information on norms and role models. Today one must add three powerful indirect or nonpersonal socialization agents: radio, movies and television. Many people learn about politics, form a vision of well-being, and develop attitudes towards others from what they see on the screen and hear through the speakers. |
The author’s chief agents include the following EXCEPT the ______.
A．family
B．group
C．school
D．internet