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