We have been told that under no circumstances_______ the office telephone for personal affairs.
| A．may we use | B．we can use | C．we could use | D．did we use |
It was quite a serious accident, _____caused by careless driving.
| A．which I think was | B．I think which was |
| C．which I think it was | D．I think which it was |
It was quite a long time_____I made it out what had happened.
| A．after | B．before | C．when | D．since |