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问题 单项选择题

较长时间接触90dB(A)以上的强烈噪声，使听力明显下降，听阈提高15～30dB(A)，离开噪声环境数小时至 20多小时后听力才能恢复，称为

A．听力适应

B．听力疲劳

C．噪声性耳聋

D．听觉外反应

E．神经性耳聋

答案

参考答案：B

选择题

互为同分异构体的物质不可能是

A．具有相同的式量

B．具有相同的结构

C．具有相同的通式

D．具有相同的化学式
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单项选择题

Flow control is a function that prevents network congestion by ensuring that (66) do not over-whelm (67) with data. There are three commonly used methods for handling network congestion. (68) is used by network devices to temporarily store bursts of excess data in memory until they can be processed. (69) are used by receiving devices to help prevent their buffers from overflowing. (70) is a flow-control scheme in which the source device requires an acknowledgment from the destination after a certain number of packets have been transmitted.

（69）是（）

A. Buffer

B. Source-quench messages

C. window

D. Windowing

E. Buffering
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