You have a Microsoft Teams Phone deployment.
You have a PBX that connects to the PSTN by using an E1/T1 Primary Rate interface (PRI).
You plan to migrate to Direct Routing by using the existing PSTN services.
What should you install upstream of the PBX?
A. a physical Session Border Controller (SBC)
B. an FXO SIP Analog Telephony Adapter (ATA)
C. a virtual Session Border Controller (SBC)
D. a Session Border Controller (SBC) in Azure
