27. People have become aware ______the fact that carbon dioxide, poison to the environment, contributes_____ air pollution.
—Do you still remember the days ______ we spent in the countryside ten years ago? —Yes,I'll never forget the experience.
All the universities have duty to ______ their students ______ of the quick development of the scientific world.
I don’t think the experiment is ______ failure. At least we have gained _______ experience.
— I’m bored. Let’s go to the cinema. — ______. I’m really busy at the moment.
To the great ___ of the citizens, no one else was infected with H1N1 except the 12 confirmed cases at that time.