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',);