A.SELECT s.学号,姓名,平均成绩FROM student s,score sc WHERE s.学号=sc.学号; GROUP BY s.学号 HAVING COUNT(*)>=5 ORDER BY 平均成绩 DESC B.SELECT 学号,姓名,AVG(成绩)FROM student s,score sc; WHERE s.学号=sc.学号 AND COUNT(*)>=5 GROUP BY 学号 ORDER BY 3 DESC C.SELECT s.学号,姓名,AVG(成绩)平均成绩 FROM student s,score sc; WHERE s.学号=sc.学号 AND COUNT(*)>=5; GROUP BYs.学号 ORDER BY 平均成绩 DESC D.SELECT s.学号,姓名,AVG(成绩)平均成绩 FROM student s,score sc; WHEREs.学号:sc.学号; GROUP BY s.学号HAVING COUNT(*)>=5ORDER BY 3 DESC