About usage of OAM in PTN device, which of the following is wrong?()

A. When AIS function is enabled and this site detects connection failure, it will insert FDI packet into customer layer in reverse direction of peer MEP site. Forwarding priority of FDI packets can be configured.

B.To test SSF alarm function, AIS function needs to be enabled.

C.When on-demand LM function is enabled, you can set local LM or peer LM function and parameters like packet forwarding priority, sending interval, report interval and test time.

D.Forwarding priority of CV packet can be set randomly.