Examine the structure of the EMPLOYEES table: EMPLOYEE_ID NUMBER Primary Key FIRST_NAME VARCHAR2(25) LAST_NAME VARCHAR2(25) HIRE_DATE DATE Which UPDATE statement is valid?（）

A. UPDATE employees SET first_name = 'John' SET last_name ='Smith' WHERE employee_id = 180;

B. UPDATE employees SET first_name = 'John', SET last_name ='Smith' WHERE employee_id = 180;

C. UPDATE employees SET first_name = 'John' AND last_name ='Smith' WHERE employee_id = 180;

D. UPDATE employees SET first_name = 'John', last_name ='Smith' WHERE employee_id = 180;