Only ____ as a volunteer ____ how important it is to grasp English.
We should consider what use can _____ such a material.
_____ on facts, the report should be reliable(可靠的).
There were so many people in the street watching the fire that the firefighters could not get _____ to the building on fire as soon as possible.
Her face went red _____ he had said.
The teacher asked an easy question, but not a proper answer _____.