For a train schedule viewer mobile app, the customer specifies a need that the user should be allowed to decide how to respond to the interrupts and notifications $($accept the call, read SMS$,$ and so on$)$ and the application should resume after the user handles the interrupt or after they choose to ignore the interrupt.

Which Non$-$Functional requirement has been discussed in this case?

Select one:a$.$ Scalabilityb. Availabilityc. Reliabilityd. Usabilitye. Portability