Warning: Holding a cell phone against your ear or storing it in your pocket may be hazardous to your health. This paraphrases a warning that cell phone manufacturers include in the small print that is often【C1】______ when a new phone is purchased. Apple, 【C2】______, doesnt want iPhones to come closer to you than 1.5 centimeters; Research In Motion, BlackBerrys manufacturer,【C3】______2.5 centimeters. If health issues【C4】______cell phone use, the implications are huge. According to a recent survey,Americans chat【C5】______cell phones 2.26 trillion minutes annually, which【C6】______ $100 billion for the wireless carriers. Epidemiologists(流行病学家)pointed out that brain cancer is a( n) 【C7】______. Overall, there has not been a(n) 【C8】______ in its incidence since cell phones arrived. But the average【C9】______an increase in brain cancer in the 20-to-29 age group【C10】______a drop for the older population. 'Most cancers have【C11】______causes,' an expert says,【C12】______she points to laboratory research that suggests low-energy radiation could damage cells that could possibly lead to cancer. Besides, children are more【C13】______ to radiation than adults, other scientists point out. Radiation that【C14】______only five centimeters into the brain of an adult will reach much deeper into the brains of children because their skulls are thinner and their brains【C15】______ more absorptive fluid. Henry Lai ,a research professor at the University of Washington,began laboratory radiation studies in 1980 and found that rats【C16】______ radio frequency radiation had【C17】______DNA in their brains. Ms. Davis recommends【C18】______wired headsets or the phones speaker. Children should text【C19】______ call, she said, and pregnant women should keep phones away from the abdomen【C20】______. 【C1】