【单选题】显示图书信息表中不同书架图书的平均价格大于50元的书架号和平均价格。能得到正确结果的SELECT语句是 A: select casename,AVG(price) <br> from bookinfo group by casename where AVG(price)>50 B: select casename,AVG(price)>50 from bookinfo group by casename C: select casename,AVG(price) <br> from bookinfo<br> having AVG(price)>50 group by casename D: select casename,AVG(price) <br> from bookinfo group by casename<br> having AVG(price)>50