问题 单项选择题

HUB是一种网络设备,它的中文名称叫 ______。

A.调制解调器
B.路由器
C.集线器
D.网桥

答案

参考答案:C

解析:HUB是大家常说的集线器,它应用于使用星型拓扑结构的网络中,连接多个计算机或网络设备。集线器又分为能动式、被动式和混合式。能动式集线器对所连接的网络介质上的信号有再生和放大的作用,可使所连接的介质长度达到最大有效长度,需要有电源才能工作,目前多数HUB为此类型。被动式集线器只充当连接器,不需要电源就可以工作,市场上已经不多见。混合式集线器可以连接多种类型线缆,如同轴电缆和双绞线。
集线器(HUB)是对网络进行集中管理的重要工具,就像树的主干一样,它是各分枝的汇集点。HUB是一个共享设备,其实质是一个中继器,而中继器的主要功能是对接收到的信号进行再生放大,以扩大网络的传输距离。在网络中,集线器主要用于共享网络的建设,是解决从服务器直接到桌面的最佳、最经济的方案。在交换式网络中,HUB直接与交换机相连,将交换机端口的数据送到桌面。使用HUB组网灵活,它处于网络的一个星型结点,对结点相连的工作站进行集中管理,不让出问题的工作站影响到整个网络的正常运行。由于HUB在网络中的重要作用,所以对于它的选型也是非常重要的。

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If you dream in color, you’re not alone: the majority of people today claim to have colorful dreams. But it wasn’t always thus. Research conducted in the early part of the last century consistently found that people reported dreaming most often in black and white.

According to Eva Murzyn at the University of Dundee, there are at least two possible explanations for this strange situation.

The first is the methods used in the researches. The early studies tended to use questionnaires(问卷), while more modern studies use dream diaries (filled in upon rising in the morning) or so-called “REM-awakening”, which involves interrupting people’s dream-filled periods of sleep to find out what they were dreaming about. People’s memories of their dreams are likely to be less accurate by using the questionnaire approach and they are more likely to reflect their beliefs about the form dreams generally take in an unclear way.

The second explanation has to do with black and white television and film. It's possible that the sudden increase in black and white film and television during the first half of the last century either affected the form of people’s dreams at that time, or affected their beliefs about the form dreams generally take.

According to Murzyn’s findings, it’s the explanation based on media exposure that carries more weight. She used both questionnaire and diary methods to study the dreams of 30 older (average age 64) and 30 younger people (average age 21).

The methodological technique made no difference to the type of dreams people reported. However, the extremely important thing was that, across both questionnaires and diaries, the older participants (who had had significant early life exposure to black and white media) reported experiencing significantly more black and white dreams over the last ten days than the younger participants (22 per cent vs. 4 per cent).

Another finding was that older participants reported black and white dreams and colorful dreams to be of equal clearness. By contrast, the younger participants reported that the quality of black and white dreams was poorer. This raises the possibility that the younger participants didn’t really have any black and white dreams at all, but were simply regarding poorly remembered dreams as black and white.

小题1:We learn from the text that ______.

A.people in the first half of the last century never had colorful dreams

B.older people are more likely to have black and white dreams

C.the dreams of younger people are always colorful

D.people today don’t have white and black dreams any more小题2:What did Murxyn do to find out the explanations for the colors in people’s dreams?

A.She applied both questionnaire and diary methods to study people’s dreams.

B.She used diary methods to record people’s dreams.

C.She chose 60 people to answer her questions about their dreams.

D.She woke people up to record the colors of their dreams.小题3:What does the underlined expression “carry more weight” in paragraph 5 mean?

A.be heavier

B.be more powerful

C.be more important

D.be more useful小题4:From Murxyn’s findings we can infer that ______.

A.both older people and younger people could report colorful dreams clearly

B.young people don’t have any black and white dreams in fact

C.the color of a person’s dream is decided by one’s age

D.it is probably the color of media that affects the color of one’s dream