Which of the Following Is not a Common Queuing Situation

Multiple Choice

Which of the following is not a common queuing situation?

A) grocery shoppers being served by checkout clerks
B) commuters slowing or stopping at toll plazas to pay highway tolls
C) machinery waiting to be repaired or maintained
D) parcel delivery truck following its computer-generated route
E) patients in a health clinic waiting to see one of several doctors