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