何谓跳频(Frequency-Hopping Spread Spectrum)?
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何谓展频(Spread Spectrum)?
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2、The immigrants spread unevenly across
The immigrants spread unevenly across the country,with()having the largest percentage of immigrants.ANortheastBthe WestCMidwestDthe South
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3、Radiation can spread a fire by ().
Radiation can spread a fire by ().Atransmitting the heat of a fire through the ship s metalBburning liquids flowing into another spaceCheated gases flowing through ventilation systemsDthe transfer of heat across an unobstructed space
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4、毒效应谱(spectrum of toxic effects)
毒效应谱(spectrum of toxic effects)
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涂布平板法(spread plate method)
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6、Fire dampers prevent the spread of fir
Fire dampers prevent the spread of fire by().AconvectionBconductionCradiationDdirect contact