27. People have become aware ______the fact that carbon dioxide, poison to the environment, contributes_____ air pollution.
A.of, to | B./, to | C.of, of | D.of, for |
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27. People have become aware ______the fact that carbon dioxide, poison to the environment, contributes_____ air pollution.
A.of, to | B./, to | C.of, of | D.of, for |