单选题When is it advisable to dump the waste toner from a technicians service vacuum？（）A When it is full.B It is not recommended.C Before performing preventative maintenance.D After each call.
题目
单选题
When is it advisable to dump the waste toner from a technicians service vacuum？（）
A
When it is full.
B
It is not recommended.
C
Before performing preventative maintenance.
D
After each call.