问题

______ over and over again, but he stillcouldn’t understand.
A:work
B:Having been explained
C:Explaining
D:It had been explained
B:Having been explained
C:Explaining
D:It had been explained
正确答案是:
同类题型
There_______ a concert to be shown in HongKong next week.
When we were young, we were often ______by Grandma to pay attention to our table manners.[ ]
What a great diversity of notebook computers!It is hard to decide, which do you _______ me?
We want to sit at the table near the window— I am sorry, but it _______ already