The CUSTOMERS table has these columns: Which statement finds the rows in the CUSTOMERS table that do not have a postal code?（）

• A、SELECT customer_id, customer_name   FROM customers   WHERE postal_code CONTAINS NULL;
• B、SELECT customer_id, customer_name   FROM customers   WHERE postal_code = '________';
• C、SELECT customer_id, customer_name   FROM customers   WHERE postal_code IS NULL;
• D、SELECT customer_id, customer_name   FROM customers   WHERE postal code IS NVL;
• E、SELECT customer_id, customer_name   FROM customers   WHERE postal_code = NULL;