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? （） A. SELECT SUM(subj1, subj2, subj3) FROM marks; B. SELECT SUM(subj1 + subj2 + subj3) FROM marks; C. SELECT SUM(subj1), SUM(subj2), SUM(subj3) FROM marks; D. SELECT MAX(subj1, subj2, subj3) FROM marks; E. SELECT MINIMUM(subj1) FROM marks; F. SELECT COUNT(std_id) FROM marks WHERE subj1 >= AVG(subj1);