多项选择题 Examine the description of the MARKS table: STD_ID NUMBER(4) STUDENT_NAME VARCHAR2(30) SUBJ1 NUMBER(3) SUBJ2 NUMBER(3) SUBJ3 NUMBER(3) SUBJ1, SUBJ2, and SUBJ3 indicate the marks (grades) obtained by a student in the three subjects. Which two statements are valid? （）

单项选择题 Examine the description of the EMPLOYEES table: Which statement produces the number of different departments that have employees with last name Smith?（）

单项选择题 Which SELECT statement should you use to extract the year from the system date and display it in the format "1998"?（）