单项选择题
What is the term for the space that exists above a drop ceiling or below a raised floor and that isused for air return？（）
A.NEMA area B.plenum area C.DAS area D.extended area E.RF special area
单项选择题 Whereshouldknownproblemareasinthesitesurveybedocumented？（）
单项选择题 TheAirMagnetpassivesitesurveytoolcanprovideRFcoveragedata，exceptforwhichparameter？（）
单项选择题 Whatapproximatesthesignalattenuationofaplasterboardwall？（）
