问题 单项选择题

局域网常用的网络拓扑结构是( )。

A.星型和环型
B.总线型、星型和树型
C.总线型和树型
D.总线型、星型和环型

答案

参考答案:D

解析:网络中的计算机等设备要实现互联,就需要以一定的结构方式进行连接,这种连接方式叫做拓扑结构,通俗地讲就是这些网络设备如何连接在一起的。目前常见的网络拓扑结构主要有以下4类:星型结构、总线型结构、环型结构、复合型结构。
星型网通过点到点链路接到中央结点的各站点组成的,通过中心设备实现许多点到点连接。在网络中,这种设备是主机或集线器。总线型网络采用单根传输线作为传输介质,所有的站点都通过相应的硬件接口直接连接到传输介质或总线上。环型结构由连接成封闭回路的网络结点组成的,每一结点与它左右相邻的结点连接。复合型结构同时综合了两种以上的拓扑结构。
局域网常用的网络拓扑结构有星型结构、环型结构、总线型结构。

问答题

Where one stage of child development has been left out, or not sufficiently experienced, the child may have to go back and capture the experience of it. A good home makes this possible, for example by providing the opportunity for the child to play with a clockwork car or toy railway train up to any age if he still needs to do so. (46)This principle, in fact, underlies all psychological treatment of children in difficulties with their development, and is the basis of work in child clinics.
The beginnings of discipline are in the nursery. Even the youngest baby is taught by gradual stages to wait for food, to sleep and wake at regular intervals and so on. If the child feels the world around him is a warm and friendly one, he slowly accepts its rhythm and accustoms himself to conforming to its demands. (47)Learning to wait for things, particularly for food, is a very important element in upbringing, and is achieved successfully only if too great demands are not made before the child can understand them.
Every parent watches eagerly the child’s acquisition of each new skill — the first spoken words, the first independent steps, or the beginning of reading and writing. (48)It is often tempting to hurry the child beyond his natural learning rate, but this can set up dangerous feeling of failure and states of anxiety in the child. This might happen at any stage. A baby might be forced to use a toilet too early; a young child might be encouraged to learn to read before he knows the meaning of the words he reads. (49)On the other hand, though, if a child is left alone too much, or without any learning opportunities, he loses his natural zest for life and his desire to find out new things for himself.
Learning together is a fruit source of relationship between children and parents. By playing together, parents learn more about their children and children learn more from their parents. Toys and games which both parents and children can share are an important means of achieving this co-operation. Building-block toys, jigsaw puzzles and crossword are good examples.
Parents vary greatly in their degree of strictness or indulgence towards their children. Some may be especially strict in money matters; others are severe over times of coming home at night, punctuality for meals or personal cleanliness. (50)In general, the controls imposed represent the needs of the parents and the values of the community as much as the child’s own happiness and well-being.

单项选择题