A.SELECT.student_name,subject1.FROM.marks.WHERE-subject1>AVG(subject1)
B.SELECT.student_name,SUM(subject1)FROM.marks.WHERE-student_name-LIKE’R%’
C.SELECT.SUM(subject1+subject2+subject3)FROM.marks.WHERE-student_name-ISNULL
D.SELECT.SUM(DISTINCT.NVL(subject1,0)),MAX(subject1)FROM.mark.sWHERE-subject1>subject2