9．
| A．take off B．mean C．how D．against E．safely |
Although we still don't know whether using mobile phones can cause cancer，we should try to use our phones（50）E．Here are some tips：
*Use a headset（耳机） or speaker．
Headsets give out much less radiation than phones．Some wireless headsets give out low-level radiation．However，you should （51）Ayour headset when you're not talking to anyone．Using a phone with a speaker will also make it safer．
*Listen more，talk less．Your phone gives out radiation when you talk or text，but not when you're listening or getting messages．
*Hold the phone away from your body when you are talking，not（52）Dyour ear．
Also，don't keep it in your pocket．
*Choosing texting over talking．Phones give out less radiation when sending texts than when making calls．Texting also keeps radiation away from your head．
*Poor signal？Stay off the phone．Fewer signal bars（信号格数） on your phone（53）Bthat the phone needs to give out more radiation to work．Make and take calls when your phone has a strong signal．
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