Which of the following are the causes of this issue?

A voice engineer is troubleshooting a phone issue. When a call is placed, the caller hears echoes of the receiver’s voice .

Which of the following are the causes of this issue? (Choose two.)
A . Jitter
B . Speed mismatch
C . QoS misconfiguration
D . Protocol mismatch
E . CRC errors
F . Encapsulation errors

Answer: A,C