The computer system suddenly_____ while he was searching for information on the Internet.
| A．broke out | B．broke up |
| C．broke in | D．broke down |
It was not long_____ he got to know it.
| A．when | B．before | C．after | D．until |
It is five days_____ we came here.
| A．when | B．before | C．as | D．since |
I have not seen him_____ he went to college.
| A．when | B．before | C．as | D．since |
They did not stop fighting_____ there was no enemy left.
| A．until | B．after | C．when | D．since |
I was about to leave my house _____the phone rang.
| A．while | B．when | C．as | D．after |