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ZigBee与蓝牙特性比较？

答案

参考答案：

功耗：ZigBee2节5号干电池可支持一个节点工作6-24个月。蓝牙功耗中等。传输率：蓝牙的数据速率为1Mb/s。ZigBee的数据速率为20～250kbps。

解答题

A、B、C、D四个数，每次去掉一个数，将其余三个数求平均数，这样计算了四次，得到下面四个数：23，26，30，33．A、B、C、D四个数的平均数是（　　）

A．26

B．27

C．28

D．29
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单项选择题

Although many people would not believe it, the mosquito is actually the most dangerous animal in Africa. While the bite of the black mamba is invariably lethal when untreated, this dreaded snake kills only a few dozen people per year. Hippopotami, with their immense strength and foul dispositions, kill hundreds of people per year in rivers and lakes, but the mosquito is still more dangerous. Mosquitoes bite hundreds of millions of people in Africa every year, and they infect over a million each year with malaria, a disease that is often fatal.
Which of the following questions would be most useful in evaluating the claim made above regarding the mosquito ？（）

A. Could a person survive an attack by a black mamba if that person received prompt medical attention

B. What criteria are used to determine which animal is the "most dangerous" animal

C. Could the incidence of mosquito bites be decreased through the judicious use of pesticides and insect repellent

D. Does malaria kill more people per year in Africa than tuberculosis

E. How does the percentage of people who survive hippopotamus attacks in Africa each year compare with the percentage of people who survive mosquito bites
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