Answer: b. Waste of a flow unit’s time
Explanation: Lean operations are a means of running an organization or firm by prioritizing on providing greater customer satisfaction while using as little resources as possible. The aim is to create value for customers and eliminating waste. The observation made by the customer is an example of waste of flow unit time as there's significant waste of time for units passing through the airport per unit time. A flow unit is the basic unit of analysis in any given scenario such as customer, phone call etc. The flow units are the customers, money, produced goods/services going through the business process per unit time.