47、回答47-57題：

　　So many people use the cell phone frequently every day．But___47___little is certain about the health effects of its use．Manufactures___48___that cell phones meet government standards for safe radio frequency radiation emission，but enough studies are beginning to document a possible___49___in rare brain tumors(腫瘤)，headaches and behavioral disorders in children to cause concern．So far,the evidence isn’t___50___ on whether the use of cell phones___51___to any increased risk of cancer．In a new trial，researchers asked 47 volunteers to___52___in a project to measure glucose(葡萄糖)consumption in the brain by scanning the brain to see how cells use energy．For both 50 minute scans，the volunteers had a cell phone___53___to each ear．During the first scan，the devices were turned off,but for the second scan，the phone on the right ear was___54___on and received a recorded-message call，although the volume was muted(消音) so the noise wouldn’t bias the results．The results of the second scan showed that the___55___0f the brain nearest to the device had higher rates of glucose consumption than the rest of the brain．The study shows that cell phones can change brain activLty,and___56___a whole new avenue for scientific inquiry,though it doesn’t say anything about whether cell-phone radiation can cause cancer．

　　A．conclusive

　　B．contributes

　　C．derive

　　D．expresses

　　E．fixed

　　F．immensely

　　G．increase

　　H．maintain

　　I．mission

　　J．participate

　　K．particular

　　L．provides

　　M．regions

　　N．surprisingly

　　O．switched

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