Answer:
C. The average time in line plus the average service time.
Step-by-step explanation:
Customer services is a skill in business that requires interactivity with customers, and an approach to gaining their trust and loyalty.
A queue is a straight line arrangement of entities. Customer service queueing system is a queue of customers, taking turns for a product or service.
The average time a customer spends in a system is equivalent to the average time on queue plus the average time for services rendered to customers before him and including him.