In the context of the MERGE statement, certain syntax rules and logical sequences must be observed:

Option B:

Correct use of the MERGE statement includes specifying the source and target correctly, and handling cases for matched and unmatched rows. This option properly structures the MERGE command with correct conditions for both matching (on prod_id) and actions (insert for unmatched, and delete under certain conditions for matched rows).

Option D:

While this option has a typographical error with "WHEN NOT NATCHED", assuming it's intended as "WHEN NOT MATCHED", it correctly describes the action for inserting into new_prices when no match is found in the target table based on the condition specified (product cost less than 200).

Options A and C contain syntax errors and logical contradictions (such as attempting to both update and delete in the same matched clause without proper separation or conditions), which are not allowed in a single WHEN MATCHED clause in Oracle SQL.