Which of these is true about undo tablespace?

Undo tablespace holds undo records that exist only for the duration of active transactions and the configured undo retention period - the data is not permanently committed user data, making it temporary in terms of its data lifecycle. Oracle internally classifies it as a distinct UNDO tablespace type, but it shares the essential characteristic of storing non-permanent, transient data rather than permanent application data.

An undo tablespace is not restricted to a single datafile; additional datafiles can be added to it as undo space requirements grow.

While undo extents are reused in a wrap-around fashion as old undo data expires, this describes internal space management behavior rather than a defining characteristic that classifies the tablespace type.