7、Every possible means ______ to prevent the air pollution, but the sky is still not clear.
After that, he knew he could __________ any emergency by doing what he could to the best of his ability.
He had told her so little that she was all at sea anyhow __________ the whole procedure.
He wrote to tell me that there was no need to worry about him and he had offered to clean the community __________ a week's accommodation.
He is teaching me French __________ my teaching him Chinese.
The committee __________ over the problem among themselves for two hours.