_______ the people have become masters of their country _______ science can really serve the people.
| A．It is only then; that |
| B．It was that; when |
| C．It is only when; that |
| D．It was when; then |
Mr. Smith，________of the ________speech，started to read a novel.
| A．tired；boring | B．tiring；bored |
| C．tired；bored | D．tiring；boring |
It was not until the teacher had explained it three times _______ how to work out the problem.
| A．did he understand | B．had he understood |
| C．that he understood | D．that he didn’t understood |
Only after my friend came ____.
| A．did the computer repair | B．he repaired the computer |
| C．was the computer repaired | D．the computer was repaired |
Dickson left his father’s firm and ____business on his own.
| A．started out | B．launched into | C．began on | D．worked at |
There is no doubt _______international cooperation is the key to dealing with cyber crime.
| A．then | B．that | C． wheather | D．this |