单项选择题
A.Laser unit
B.Developer unit
C.Charge assembly
D.Fuser assembly
单项选择题 Acustomerhasinstalledanewcomputerontheirnetwork.Theycanprinttotheprinterbuttheoptionforduplexprintingisnotavailable.Allothercomputershavetheoption.Whichofthefollowingisthecauseoftheproblem？（）
单项选择题 Whenisitadvisabletodumpthewastetonerfromatechniciansservicevacuum？（）
单项选择题 HowmanyCCDsarelocatedinasinglepassduplexADF？（）