When placing a call from an IP Phone to another IP Phone, how isringbackgenerated??

When placing a call from an IP Phone to another IP Phone, how isringbackgenerated??

A.
CallManager generates an RTP stream to playringbackon the originated phone.

B.
CallManager sends a command to the originating IP Phone to playringbacklocally.

C.
The originating IP Phone playsringbacklocally until the RTP stream has been established.

D.
The phone is connected to an audio file server that generates theinbandringbacktones.