A. SELECT MAX (gpa) FROM student _ grades WHERE gpa IS NOT NULL;
B. SELECT (gpa) FROM student _ grades GROUP BY semester_end WHERE gpa IS NOT NULL;
C. SELECT MAX (gpa) FROM student _ grades WHERE gpa IS NOT NULL GROUP BY semester_end;
D. SELECT MAX (gpa) GROUP BY semester_end WHERE gpa IS NOT NULL FROM student _ grades;
E. SELECT MAX (gpa) FROM student _ grades GROUP BY semester_end WHERE gpa IS NOT NULL;