为自己加油

数据库有一个试卷表,希望找出试卷平均得分小于 90 的所有试卷( ) 。

A.SELECT * FROM paper group by score having sum  ( score ) < 90;
B.SELECT * FROM paper group by score having avg  ( score ) < 90;
C.SELECT * FROM paper group by score having max  ( score ) < 90;
D.SELECT * FROM paper group by score having mid  ( score ) < 90;