关系SC(Sno，Cno，Grade)表示学号，课程号，成绩。现要查询平均分在90分以上的学生的学号和平均成绩，正确的语句是______。

A．SELECT Sno，AVG(Grade)
FROM SC
WHERE AVG(Grade)＞=90
GROUP BY Sno
B．SELECT Sno，AVG(Grade)
FROM SC
GROUP BY Sno
HAVING AVG(Grade)＞=90
C．SELECT Sno，AVG(Grade)
FROM SC
WHERE AVG(Grade)＞=90
ORDER BY Sno
D．SELECT Sno，AVG(Grade)
FROM SC
GROUP BY Cno
HAVING AVG(Grade)＞=90