Examine the command：   ALTER DATABASE ADD SUPPLEMENTAL LOG DATA （PRIMARY KEY） COLUMNS；   What does the command accomplish？（）

• A、Creates an additional copy of the database online redo log files. 
• B、Stores the primary key column values of each row involved in a DML operation in the online redo log files. 
• C、Stores the primary key column values of each row involved in a DML operation in the supplemental log files. 
• D、Stores the old and new primary key column values of each row involved in a DML operation only when the primary key is modified in the online redo log files.