13. The struggle against the bird flu and the suffering _________ brought about have become a big concern across the world.
| A．which has | B．it is | C．it has | D．what is |
There ____ no buses, we had to walk home after work yesterday.
| A．was | B．were | C．being | D．had |
—Why not take my car to the museum instead of walking?
— No, thanks. ____.
| A．I'm used to | B．I’m able to | C．I'm about to | D．I've got to |
_________ for the free tickets, I would not have gone to the films so often.
| A．If it is not | B．Were it not | C．Had it not been | D．If they were not |
I think they failed to accomplish the task, ______?
| A．do I | B．don't I | C．did they | D．didn't they |
You might as well expect a river to flow backward ____ us carrying out the plan.
| A．than stop | B．as to stop | C．as stop | D．so as to stop |