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网络OSI参考模型下三层是（）
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电气式压力计是将（）转换成（）进行传输及显示的仪表。
用电流表内接法测得待测电阻值为R1，用电流表外接法测得待测电阻值为R2，若待测电阻的真实值为R0，则（）
简述战略人力资源管理的基本特征。
案例分析题The natives of La Gomera an carry on long-distance conversations by whistling. For ordinary conversation they speak Spanish. But when they need to speak over a distance， and ordinary speech is impossible， they use the silbo， the name of a whistled form of speech. La Gomera is one of the smaller Canary Islands. It is very mountainous， for it was once a volcano. The island is almost circular in shape， with a high peak in the center. From this peak， deep， narrow valleys are separated by rocky ridges. So in spite of the island’s small size， walking from one place to another may be a slow and difficult job. That is why the silbo is so useful to the natives. A message can easily be whistled over a couple of miles， while to travel that same distance on foot might take an hour. A good whistler can be heard and understood five miles away. His whistling can be heard even farther away when conditions are favorable---when there is little or no wind. I was informed that the record is about nine miles. Anyone who has heard a first-class whistler will agree that this figure is quite possible. Not only does a whistle carry father than a shout， but it is easier to understand. When a person shouts， he cannot pronounce his words well. But in whistling， this problem does not exist. If a whistle is heard at all， it will be heard clearly. Many methods of whistling are used at La Gomera. The only one never used is the common lip whistle， because it is not loud enough. Usually a whistler inserts one or two fingers， or a bent finger， into his mouth. He keeps the front of his tongue still， and his lips spread and stiff. With some practice， this method of whistling can make a tone of astonishing loudness and clearness， with great carrying power and a range of about three octaves （八音度）. In the eastern part of the island， most whistlers whistle in the upper range. On other parts of the island， they whistle in the lower range. Some whistlers do not use their fingers at all. Instead， they form a curve in the front part of the tongue which touches the upper front teeth. They then use their hands to form a kind of megaphone. There is nothing very unusual about these methods of whistling. Anyone with a good set of teeth can learn in couple of days to produce a noise that sounds much like a steam whistle. The really remarkable thing is that his simple noise can be used as a language. Compared with shouting， whistling has the following features except being （）.
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