They considered___ a computer, which was considered ___ a great help in their work.

A．to buy；to be

B．buying；being

C．to buy；being

D．buying；to be

在查询设计器中，选定“杂项”选项卡中的“无重复记录”复选框，等效于执行SQL SELECT语句中的（ ）。

A． WHERE

B． JOIN ON

C． ORDER BY

D． DISTINCT