Examine the following RMAN script：   RMAN> run { debug on；  allocate channel c1 type disk； backup datafile 5； }   Which statement describes the purpose of the script？（）  

• A、 The data file is checked for physical corruption and backed up if found clean.
• B、 The backup of data file 5 is performed and the interactive messages during the backup are suppressed.
• C、 The existing backup for the data file is checked and the backup is performed if there are changes in the data file after the last backup.
• D、 The backup of data file 5 is performed and all SQL statements that are executed during RMAN compilation and their results are displayed