Examine the command： &

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

• ACreates an additional copy of the database online redo log files. 
• BStores the primary key column values of each row involved in a DML operation in the online redo log files. 
• CStores the primary key column values of each row involved in a DML operation in the supplemental log files. 
• DStores 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.