Ⅰ.阅读理解
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People love cellphones，which is why nine in ten Americans own one.But does heavy use of cellphones pose a risk of cancer? This question has caused controversy for many years.A new study in rats now augments those concerns.Its data linked longterm，intense exposure to radiation from cellphones with an increased risk of cancer in the heart or brain.The results have yet to be confirmed，the authors note.
Indeed，although the rat study found a link between cellphone radiation and cancer，it offers no clues to why such a link might exist，notes Jonathan Samet.He teaches preventative medicine and directs the Institute for Global Health at the University of Southern California in Los Angeles.Still，he calls the new study's findings “significant”．They could lead to studies researching how cellphone radiation might cause cancer，he says.
Phone signals are relayed between cell towers and cellphones via radio waves.This radio frequency—or RF— radiation is a type known as nonionizing(非电离的)．Unlike Xrays，nonionizing radiation does not deposit enough energy into cells to release electrons from atoms or molecules，producing ions. So it tends to be far
