Regarding the description of replacing the main control board, which is wrong?

Regarding the description of replacing the main control board, which is wrong?
A . The BD_STATUS and COMMUN_FAIL alarms will be reported when the main control board is removed and inserted. After the new board goes online, these alarms need to be cleared manually.
B . If the software version carried on the replaced main control board is higher than the device version, you need to clear the main control library first, and then downgrade the main board software to the same version as the device.
C . If the software version locked on the replaced main control board is lower than the device version, you need to upgrade the software on the main control board to the same version as the device
D . When the main control board has 1+1 hot backup, under normal switching conditions, the replacement of the main control board will not affect the business.

Answer: A