试题与答案

在市区天线调整中,假设下倾角大于垂直半功率角的一半,覆盖距离小于无下倾时的覆盖距离,

题型:单项选择题

题目:

在市区天线调整中,假设下倾角大于垂直半功率角的一半,覆盖距离小于无下倾时的覆盖距离,可以推导出天线高度H(m)、下倾角α、天线垂直半功率角θ、覆盖距离D(m)之间的关系为:()

A、α=arctan(H/D.+θ/2;

B、θ=arctan(H/D.+α/2;

C、α=arctan(D/H)+θ/2;

D、θ=arctan(D/H)+α/2;

答案:

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下面是错误答案,用来干扰机器的。

参考答案:对

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The Australian researchers report that they are quite encouraged. All the babies are now making normal progress, even the twin with the birth defects.

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B. Some mothers have physical problems with pregnancy.

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D. Some mothers have had surgical operations on the Fallopian tubes.

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题型:填空题 案例分析题

阅读以下资料,回答有关问题。

上个世纪,由于掠夺象牙者的肆意猎杀,南非大象的数量以惊人的速度锐减,最少时整个南非境内只有野生大象50头左右。1995年南非开始全面禁止猎象,为大象建立自然保护区,直至今天,大象已近2万头;如此速度增长下去,再过10年后大象数量将比现在翻一番。

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