Examine the structure of the EMPLOYEES table: EMPLOYEE_ID NUMBER Primary Key FIRST_NAME VARCHAR2(25) LAST_NAME VARCHAR2(25) Which three statements inserts a row into the table? （）

• A、INSERT INTO employees VALUES (NULL, 'JOHN','Smith');
• B、INSERT INTO employees( first_name, last_name) VALUES ('JOHN','Smith');
• C、INSERT INTO employees VALUES ('1000','JOHN','NULL');
• D、INSERT INTO employees(first_name,last_name, employee_id) VALUES ('1000, 'john','Smith');
• E、INSERT INTO employees (employee_id) VALUES (1000);
• F、INSERT INTO employees (employee_id, first_name, last_name) VALUES ( 1000, 'john',");