Which statement is true about the UNDO_RETENTION parameter when retention guarantee is not enabled（）

• A、It is the time period after which the undo data becomes obsolete.
• B、It is the time period after which the committed undo data would be transferred to a temporary tablespace.
• C、It is the minimum time period up to which the committed undo data would be retained if free undo space isavailable.
• D、It is the time period after which the undo data is transferred to the Flash Recovery Area to provide readconsistency.