Consider the following scenario for your database: - Backup optimization is enabled in RMAN. - The recovery window is set to 7 days in RMAN. - The most recent backup to disk for the TOOLS tablespace was taken on November 3, 2007. - The TOOLS tablespace is read-only since November 4, 2007. On November 23, 2007, you issue the RMAN command to back up the database to disk. Which statement is true regarding the backup of the TOOLS tablespace?（）
- A The RMAN backup fails because the TOOLS tablespace is read-only
- B The RMAN skips the backup of the tablespace because backup optimization is enabled
- C The RMAN makes backup because optimization can be enabled only for backups to disk
- D The RMAN makes the backup because no backup of the tablespace exists within the seven day window