Refer to the exhibit The SDP offer/answer has been completed successfully but there is no DTMF when users press keys. What is the cause of the issue?
A. DTMF was negotiated properly in these messages.
B. G.729 rather than G.711ulaw was negotiated.
C. Payload type 110 was negotiated rather than type 101.
D. DTMF was not negotiated on the call.
