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问题 填空题

初春时节，柳树发芽，你可以这一根柳条，把皮和芯拧松，抽出木芯，用刀把嫩皮的两端修齐，就制成了“柳笛”．用力吹柳笛就发出响声．该响声是由于______的振动而产生的．并以______的形式传播到人们的耳朵里．

答案

（1）柳笛中有空气．用力吹时，柳笛内部的空气柱振动，发出声音．

（2）声音是以声波的形式向外传播的．

故答案为：空气柱；声波

单项选择题

When you think of the Internet, you probably think of ".com." Just what do those three letters at the end of a World Wide Web address mean Every computer that hosts data on the Internet has a (71) numerical address. For example, the numerical address for the White House is 198.137.240.100. But since (72) people want to remember long strings of numbers, the (73) was developed. It is a critical part of the Internet’s technical infrastructure, correlates a numerical address to a word. To (74) the White House website, you could type its numerical address into the address box of your web browser. But most people prefer to use "www.whitehouse.gov." In this case，the domain name is (75) .

（72）处填（）。

A．most

B．more

C．few

D．every
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名词解释

气流介质分级
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