The provided SQL statement is an update statement that involves a subquery which is correlated to the main query.
* A. The subquery is executed before the UPDATE statement is executed. (Incorrect) This statement is not accurate in the context of correlated subqueries. A correlated subquery is one where the subquery depends on values from the outer query. In this case, the subquery is executed once for each row that is potentially updated by the outer UPDATE statement because it references a column from the outer query (o.customer_id).
* B. All existing rows in the ORDERS table are updated. (Incorrect)
Without a WHERE clause in the outer UPDATE statement, this would typically be true. However, the correctness of this statement depends on the actual data and presence of matching customer_id values in both tables. If there are rows in the ORDERS table with customer_id values that do not exist in the CUSTOMERS table, those rows will not be updated.
* C. The subquery is executed for every updated row in the ORDERS table. (Correct) Because the subquery is correlated (references o.customer_id from the outer query), it must be executed for each row to be updated in the ORDERS table to get the corresponding cust_last_name from the CUSTOMERS table.