I always leave things about my son up to himself ______his decision is wrong, for I think he can learn more from failure.
| A．in case | B．even if | C．unless | D．until |
A number of methods been used, but the number of animals still small in the forest.
| A．have; is | B．has; is |
| C．have; are | D．has; are |
If ,the experiment will be successful.
| A．do carefully. | B．did carefully. |
| C．carefully done. | D．doing carefully. |
such heavy pollution already, It may now be too late to clean up the river.
| A．Suffering. | B．Having suffered. | C．To suffer. | D．Suffered. |
The spokesman didn’t make clear why the president failed to attend the conference.
| A．this. | B．that. | C．it. | D．what. |
One may never know the of knowledge without being educated.
| A．power. | B．force. | C．energy. | D．strength. |