单项选择题
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 (1) when a new phone is purchased. Apple, (2) , doesn’t want iPhones to come closer to you than 1.5 centimeters; Research In Motion, BlackBerry’s manufacturer, (3) 2.5 centimeters.
If health issues (4) cell phone use, the implications are huge. According to a recent survey, Americans chat (6) cell phones 2.26 trillion minutes annually, which (6) $109 billion for the wireless carriers. Epidemiologists (流行病学家) pointed out that brain cancer is a(n) (7) . Overall, there has not been a(n) (8) in its incidence since cell phones arrived. But the average (9) an increase in brain cancer in the 20-to-29 age group (10) a drop for the older population.
"Most cancers have (11) causes," an expert says, (12) she points to laboratory research that suggests low-energy radiation could damage cells that could possibly lead to cancer.
Besides, children are more (13) to radiation than adults, other scientists point out. Radiation that (14) 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 (15) more absorptive fluid.
Henry Lai, a research professor at the University of Washington, began laboratory radiation studies in 1980 and found that rats (16) radio frequency radiation had (17) DNA in their brains.
Ms. Davis recommends (18) wired headsets or the phone’s speaker. Children should text (19) call, she said, and pregnant women should keep phones away from the abdomen (20)
A. using
B. to use
C. use
D. to using