资格英语-托福分类模拟题练习十八.doc,relativelyharmlessamountsofionizingradiation,knownasbackgroundradiation,fromnaturalsourcessuchassoilandrock•However,othertypesofionizingradiation--x-rays,ultravioletradiationfromthesun,andalpha,beta,andgammaradiationemittedbyradioactiveisotopes--,suchasthebonemarrow,wherebloodcellsaremade,andthedigestivetract,<,whichcausesvictimsdirectharmintheformofbums,miscarriages,eyecataracts,sometypesofleukemia,orcancersofthebone,thyroid,breast,skin,•、Accordingtothepassage,
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