某网站的数据库有一个成绩表myscore，希望找出成绩表中平均得分小于90的所有试卷（)。A、select

某网站的数据库有一个成绩表myscore，希望找出成绩表中平均得分小于90的所有试卷()。

A、select paper_id from myscore where sum(score)< 90 group by paper_id

B、select paper_id from myscore group by paper_id having avg(score)< 90

C、select paper_id from myscore where avg(score)<90

D、select paper_id from myscore where avg(score)<90 group by paper_id