关系数据库管理系统能实现的专门关系运算包括( )。

A．选择、投影、连接

B．分组、索引、排序

C．删除、更新、追加

D．显示、打印、制表

--- Where did you meet him for the first time?

--- Maybe it is in the museum     we listened to the lecture       we got to know each other.

A．that; that

B．where; that

C．which; that

D．that; which