有关系S(S#,SNAME,SAGE),C(C#,CNAME),SC(S#,C#,GRADE)。若要查找分数(grade)不及格的学生姓名(sname),则以上正确的有?( )
A.
SELECT sname FROM s, sc WHERE grade<60
B.
SELECT sname FROM s WHERE sno IN(SELECT Cno FROM sc WHERE grade<60)
C.
SELECT sname FROM s, sc WHERE s.sno=sc.sno AND grade<60
D.
SELECT sname FROM s, sc WHERE s.sno=sc.sno OR grade<60