Which statements are true about graceful Routing Engines switchover (GRES)?

Which statements are true about graceful Routing Engines switchover (GRES)?

A.
Configuration on both Routing Engines must be synchronized.

B.
The backup Routing Engine cannot be managed through IP address because RPD does not
run on backup the Routing Engine.

C.
Different hostnames must be configured on both Routing-Engines.

D.
Both Routing-Engines are managed through a single out-of-band-management IP address.