在 SQL Server 中,以下哪个是查询指定列平均值的关键字?
选项：

A:SELECT AVG(column_name) FROM table_name GROUP BY column_name;
B:SELECT MAX(column_name) FROM table_name GROUP BY column_name;
C:SELECT MIN(column_name) FROM table_name GROUP BY column_name;
D:SELECT COUNT(column_name) FROM table_name GROUP BY column_name;