Which dial plan scenario may require PSTN trunks for outbound calls? Select exactly 1 answer(s) from the following:

A.
A subset of the employees, the auto attendant or receptionist, and the voice-mail system have direct inward dial numbers, and the remaining employees do not have direct inward dial numbers.

B.
All the employees, the auto attendant or receptionist, and the voice-mail system have direct inward dial numbers using digital interfaces.

C.
All the employees, the auto attendant or receptionist, and the voice-mail system have direct inward dial numbers using analog trunks.