北京国基RADWIN无线网桥调试时出现一声较长蜂鸣，说明是（）
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正电子发射断层成像术（PET）被广泛应用于注意力脑机制的研究。
A. 正确
B. 错误
The ash content of a fuel oil is significant to the operating engineer because it （）
A. is an indication of the amount of noncombustible material present in the oil
B. indicates the quantity of energy released by burning a unit amount of the fuel
C. is useful for determining proper atomization temperatures
D. reflects the overall thermal efficiency of the fuel oil service system
资料评价的质量指标不包括（）
A. 准确性
B. 时效性
C. 可靠性
D. 广泛性
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