将下列单词或词组填入空格，每空格限填一词，每个单词或词组只能填一次。
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 ____.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 ____ your 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 ____ your 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（信号数） on your phone ____ that the phone needs to give out more radiation to work. Make and take calls when your phone has a strong signal.
