单项选择题
When installing a security system， which of the following connectors would be used to connect the security system to the telephone service demarcation？（）
A.RJ-31x B.RJ-11 C.RS-232 D.DB-9
单项选择题 Whichofthefollowingdoesanastronomicaltimeclockdo？（）
单项选择题 Wiresthatareinstalledinairreturnsaboveaceilingmustbe（）
单项选择题 Whichofthefollowingistherecommendedplacementoftherearsurroundspeakersina5.1surroundinstallation？（）
