在SQL Server 2000中，分别统计表STUDENT1中学生不同年龄的人数和总平均分。在查询分析器中执行______

A．SELECT "统计" AS 类别,NL AS年龄, COUNT (XB) AS 人数,AVG (CJ) AS 总平均分 FROM STUDENT1 GROUP BY XB
B．SELECT "统计" AS 类别,NL AS年龄, COUNT (XB) AS 人数,AVG (CJ) AS 总平均分 FROM STUDENT1 GROUP BY NL
C．SELECT "统计" AS 类别,NL AS年龄, COUNT (XB) AS 人数,MAX (CJ) AS 总平均分 FROM STUDENT1 GROUP BY NL
D．SELECT "统计" AS 类别, NL AS年龄, COUNT (XB) AS 人数,MIN (CJ) AS 总平均分 FROM STUDENT1 GROUP BY NL