A. MERGE INTO <> USING <> WHEN MATCHED THEN UPDATE ------ WHEN NOT MATCHED THEN INSERT -------

B. MERGE <> USING <> WHEN MATCHED THEN UPDATE ------ WHEN NOT MATCHED THEN INSERT -------

C. MERGE INTO <> USING <> WHEN EXISTS THEN UPDATE ------

D. MERGE INTO <> USING <> WHEN NOT MATCHED THEN INSERT ------

Both A and D