Which dial plan scenario may require PSTN trunks for outbound calls?

A.
All the employees, the auto attendant or receptionist, and the voiceE-mail system nave direct inward dial numbers using analog trunks.

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

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