现有书目表book,包含字段:价格price(float),类别type(char);现在查询各个类别的平均价格、类别名称,以下语句正确的是()
A.selectavg(price),typefrombookgroupbytype
B.selectcount(price),typefrombookgroupbyprice
C.selectavg(price),typefrombookgroupbyprice
D.selectcount(price),typefrombookgroupbytype