25. Thirty years ago this month，China's leaders launched an economic revolution.___________the door to free market reforms and foreign trade．
| A．to open | B．opened | C．opening | D．having opened |
The book is not easy.____ it's rather difficult.
| A．On the one hand | B．On the contrary |
| C．On the other hand | D．On the other contrary |
The number of the employees has grown from 1,000 to 1,200. This means it has risen ____20 percent.
| A．by | B．at | C．to | D．with |
He spoke loudly ____ the audience could hear him clearly.
| A．so | B．that | C．so that | D．in order to |
What idea can a man who is blind from birth have_____ color?
| A．in | B．/ | C．with | D．of |
I don' t know ____ to stay at home or go out.
| A．whether | B．if | C．how | D．where |