MCQOPTIONS
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				| 1. | 
                                    A considerable part of the harmful ultraviolet radiation of the sum does not reach the earth surface, because of the fact that, there is a layer of __________ high above earth's atmosphere, which absorbs it. | 
                            
| A. | hydrogen | 
| B. | carbon dioxide | 
| C. | ozone | 
| D. | none of these | 
| Answer» D. none of these | |