单项选择题

Once upon a time they used to mine coals in these valleys.

A．At a time
B．At one time
C．At times
D．At the time
<上一题 目录 下一题>
热门 试题

单项选择题
A well-written composition need good choice of words and clear organization among other things.
A．calls on
B．calls for
C．calls up
D．calls off
单项选择题
Our teacher notified us that there would be test on Monday.
A．advised
B．assured
C．informed
D．disclosed
相关试题