A.SELECT COUNT() AS 人数,AVG(YEAR(出生年月)) AS 平均年龄 FROM Students;
B.SELECT COUNT(*) AS 人数,AVG(YEAR(出生年月)) AS 平均年龄 FROM Students;
C.SELECT COUNT(*) AS 人数,AVG(Year(Date())-Year(出生年月)) AS 平均年龄 FROM Students;
D.SELECT COUNT() AS 人数,AVG(Year(Date())-Year(出生年月)) AS 平均年龄 FROM Students;