单项选择题
Wires that are installed in air returns above a ceiling must be（）
A.fire proof B.fiberglass coated C.plenum rated D.teflon coated
单项选择题 Whichofthefollowingistherecommendedplacementoftherearsurroundspeakersina5.1surroundinstallation？（）
单项选择题 Ifthespeakersinaninstallationareoutofphase，thismeansthat（）
单项选择题 WhichofthefollowingcablingwouldbeMOSTcommonlyusedwithdigitalvolumecontrols？（）
