Which statement is true about the loss of a data file belonging to the default undo tablespace?

The database cannot remain open, even in read-only mode, without its default undo tablespace because it cannot ensure consistent reads or transaction integrity.

If a data file for the default undo tablespace is lost, the database cannot perform rollbacks or ensure read consistency, leading to an unopenable state from which it can only be recovered after being placed in MOUNT state.

Without a functional undo tablespace, no DML operations can be executed, and even querying might yield inconsistent results, rendering the database inoperable for normal use.

While noncommitted transactions will be lost due to the absence of their undo information, this statement describes a consequence rather than the specific state of the database itself.

Although the instance might abort, the database's ultimate state preventing it from being opened and necessitating recovery is the MOUNT state, which allows for recovery operations to be performed.