Cellphonesareeasilythemostpopularinthetwenty-firstcentury.Acellphonehasnowiresandcanbecarriedeverywhereeasily.Wecanusecellphonestogetnews,games,musicandchat.Somecellphonesaredesignedlikeacomputerprogram.However,everycoinhastwosides.Cellphoneshavealotofinvisiblerayswhichcancausecancer.WhatImeanbyinvisibleraysarewhatwecallalpharaysandbetarays,etc.Theycancausecancer.So,weshouldusecellphonesreasonablyandeffectively. 　　百度知道上有了,这个写的比较好的.