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问题 单项选择题

计算2007年某地的婴儿死亡率，分母应为2007年（）。

A.年初0岁组人口数

B.年中0组人口数

C.年末0岁组人口数

D.活产数

E.平均人口数

答案

参考答案：D

解析：婴儿死亡率指某年某地活产儿中不满1周岁婴儿的死亡频率。计算公式为：婴儿死亡率＝×1000‰，故选项D正确。

单项选择题

急性胰腺炎发病与饮食的关系是

A．常发生在进油腻食后
B．过食、饮酒后发生
C．腹痛在剧烈活动后发生
D．持续性腹痛阵发加重
E．转移性疼痛
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单项选择题

Although a given waveform may contain frequencies over a very broad range, as a practical matter any transmission system will be able to accommodate only a limited band of （） . This, in turn, limits the data rate that can be carried on the transmission （） . A square wave has an infinite number of frequency components and hence an infinite （） .However, the peak amplitude of the kth frequency component, kf, is only 1/k, so most of the （） in this waveform is in the first few frequency components. In general, any digital waveform will have （） bandwidth. If we attempt to transmit this waveform as a signal over any medium, the transmission system will limit the bandwidth that can be transmitted.

so most of the （） in this waveform is in the first few frequency components.

A．frequency

B．energy

C．amplitude

D．phase
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