Answer: Inseparability
Explanation: Inseparability refers to the characteristic of a service. It states that production and consumption of the service could not be separated. In simple words, if the service is provided by any service provider then it must be consumed.
For example if a doctor is providing service then it must that there would be a patient to consume it.
In the given case, Martha could not provide the service if the customers are not there. Hence we can conclude that the correct option is C.