用SQL语言检索选修课程在5门以上(含5门)的学生的学号、姓名和平均成绩,并按平均成绩降序排序,正确的命令是
A.SELECT学号,姓名,平均成绩FROMS,SC; WHERE学号=S学号; GROUP BY 学号HAVING GOUNT(*)>=5 ORDER BY 平均成绩 DESC
B.SELECT 学号,姓名,AVG(成绩)FROMS,SC; WHERE 学号=S学号 AND COUNT(*)>=5; GROUP BY 学号 ORDER BY 3 DESC
C.SELECT 学号,姓名,AVG(成绩)平均成绩FROM S,SC; WHERE 学号=S学号 AND COUNT(*)>=5; GROUP BY 学号ORDER BY平均成绩DESC
D.SELECT 学号,姓名,AVG(成绩)平均成绩FROM S,SC; WHERE 学号=S学号; GROUP BY 学号 HAVING COUNT(*)>=5 0RDER BY 3 DESC