单项选择题

We（）on it for many hours but we have not yet reached any concinsion.

A．work
B．have been worked
C．have been working
D．are working

<上一题 目录 下一题>
热门 试题

单项选择题
This room had but a single window,（）were kept closed when it was not in use.

A．which its shutters
B．its shutters of which
C．the shutters of which
D．which shutters
相关试题