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.select avg(price),type from book group by type B.select count(price),type from book group by price C.select avg(price),type from book group by price D.select count(price),type from book group by type