--- Thanks a lot for your book. I found it very interesting.

--- ______. I’m glad you enjoyed it.

A．All the best

B．It is nothing

C．No thanks

D．Very well

关系数据库管理系统能实现的专门关系运算包括( )。

A．排序、索引、统计

B．选择、投影、连接

C．关联、更新、排序

D．显示、打印、制表