How is it possible that queues occur even when the utilization is lower than 100%? Group of answer choices
a. Larger batch sizes cause some units to be waiting while others are worked on
b.Variability causes the system to sometimes sit idle (but this time cannot be stored) and be really busy at other times (leading to queues)
c.Because employees are lazy and wait for a queue to occur before they start working
d. Long setup times can increase the utilization to above 100% at which point the system is no longer workable

The answer is: B)Variability causes the system to sometimes sit idle (but this time cannot be stored) and be really busy at other times (leading to queues)

Explanation:

Variability is present everywhere. No production process is 100% perfect, some may be very close to being 100%, but not quite. When some type of variability stops at least one production process, queues might happen once the production restarts since you cannot store time.

For example, this is specially true for services, if you only use 70% of the rooms of a hotel today, you cannot use 130% of the rooms tomorrow.