What two are the prerequisites for enabling Flashback Database?

What two are the prerequisites for enabling Flashback Database? (Choose two)

A.
The database must be in ARCHIVELOG mode

B.
The database must be in MOUNT EXCLUSIVE mode

C.
The database must be opened in RESTRICTED mode

D.
The database instance must be started in the NOMOUNT state

E.
The database instance must have the keep buffer pool defined