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’,‘’);