Recentresearchhasclaimedthatanexcessofpositiveionsintheaircanhaveanilleffectonpeople‘sphysicalorpsychologicalhealth.WhatarepositiveionsWell，theairisfullofions，electricallychargedparticles，andgenerallythereisaroughbalancebetweenthepositiveandthenegativecharged.Butsometimesthisbalancebecomesdisturbedandalargerproportionofpositiveionsarefound.Thishappensnaturallybeforethunderstorm，earthquakeswhenwindssuchastheMistral，HamsinorSharavareblowingincertaincountries.Oritcanbecausedbyabuild-upofstaticelectricityindoorsfromcarpetsorclothingmadeofman-madefibres，orfromTVsets，duplicatorsorcomputerdisplayscreens.
Whenalargenumberofpositiveionsarepresentintheairmanypeopleexperienceunpleasanteffectssuchasheadaches，fatigue，irritability，andsomeparticularlysensitivepeoplesuffernauseaorevenmentaldisturbance.Animalsarealsoaffected，particularlybeforeearthquakes，snakeshavebeenobservedtocomeoutofhibernation，ratstofleefromtheirburrows，dogshowlandcatsjumpaboutunaccountably.ThishasledtheUSGeographicalSurveytofundanetworkofvolunteerstowatchanimalsinanefforttoforeseesuchdisastersbeforetheyhitvulnerableareassuchasCalifornia.
Conversely，whenlargenumbersofnegativeionsarepresent，thenpeoplehaveafeelingofwell-being.Naturalconditionsthatproducetheselargeamountsarenearthesea，closetowaterfallsorfountains，orinanyplacewherewaterissprayed，orformsaspray.Thisprobablyaccountsforthebeneficialeffectofaholidaybythesea，orinthemountainswithtumblingstreamsorwaterfalls.
Toincreasethesupplyofnegativeionsindoors，somescientistsrecommendtheuseofionisers：smallportablemachines，whichgeneratenegativeions.Theyclaimthationisersnotonlycleanandrefreshtheairbutalsoimprovethehealthofpeoplesensitivetoexcesspositiveions.Ofcourse，therearethedetractors，otherscientists，whodismisssuchclaimsandareskepticalaboutnegative/positiveionresearch.Thereforepeoplecanonlymakeuptheirownmindsbyobservingtheeffectsonthemselves，oronothers，ofanegativerichorpoorenvironment.Afterallitisdebatablewhetherdependingonseismicreadingstoanticipateearthquakesismoreeffectivethanwatchingthecat.
1.Inaccordancewiththepassage，staticelectricitycanbecausedby___.
A.usinghome-madeelectricalgoods.
B.wearingclothesmadeofnaturalmaterials.
C.walkingonartificialfloorcoverings.
D.copyingTVprogramsonacomputer.
2.Whateffectdoesexceedingpositiveionizationhaveonsomepeople
A.Theythinktheyareinsane.
B.Theyfeelratherbad-temperedandshort-fussed.
C.Theybecomeviolentlysick.
D.Theyaretootiredtodoanything.
3.Ahighnegativeioncountislikelytobefound___.
A.nearapoundwithawaterpump.
B.closetoaslow-flowingriver.
C.highinsomebarrenmountains.
D.byarotatingwatersprinkler.
4.Somescientistsbelievethat___.
A.watchinganimalstoanticipateearthquakesismoreeffectivethandependingonseismography.