关系SC(Sno，Cno，Grade)表示学号，课程号，成绩。现要查询最高分在91分以上的学生的学号和平均成绩，正确的语句是______。

A．SELECT Sno，MAX(Grade) FROM SC WHERE MAX(Grade)＞=91 GROUP BY Sno
B．SELECT Sno，MAX(Grade) FROM SC GROUP RY Sno HAVING MAX(Grade)＞=91
C．SELECT Sno，MAX(Grade) FROM SC WHERE MAX(Grade)＞=91 ORDER BY Sno
D．SELECT Sno，MAX(Grade) FROM SC GROUP BY Cno HAVING MAX(Grade)＞=91