When the LTE network deployment VOLTE, which of the following scenarios voice can also be solved through CSFB in? (Multiple choice)
A . IMS network guides user CSFB through parameter configuration
B . The VOLTE call flow is abnormal, and the terminal connects to the call through the CS network.
C . When an emergency call is made, the VOLTE user can dial the emergency number through CSF
E . Terminal autonomous CSFB
Answer: ABCD