When is the UNDO_RETENTION parameter value ignored by a…

When is the UNDO_RETENTION parameter value ignored by a transaction?

A.
when the data file of the undo tablespace is autoextensible

B.
when there are multiple undotablespaces available in a database

C.
when the undo tablespace is of a fixed size and retention guarantee is not enabled

D.
when Flashback Database is enabled