| We must do something to _____ the factories sending out poisonous gases so as to keep the city_____. |
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| A. keep; being polluted B. keep; from being polluted C. prevent; being polluted D. prevent; from being polluted |
| As you know,reading in the sun _____ your eyes. |
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| A. is harm to B. is harmful to C. does harmful to D. harm to |