阅读理解It’struethatteensdon’tgetenoughsleep，butchangingtheschoolstartingtimewouldhaveachaoticeffectandthroweveryoneoffbalance.Scientistshaveshownthatteensaremoreactivelateratnightth

　　阅读理解

　　It’struethatteensdon’tgetenoughsleep，butchangingtheschoolstartingtimewouldhaveachaoticeffectandthroweveryoneoffbalance.

　　Scientistshaveshownthatteensaremoreactivelateratnightthanchildrenandadults，somost

　　teensareprobablystayinguplaterforwhateverreasons.“Theresearchersmeasuredthepresenceofthe

　　sleeppromotinghormone(荷尔蒙)inteenagers’saliva(唾液)atdifferenttimeoftheday.Theylearned

　　thatthehormonelevelsriselateratnightthantheydoinchildrenandadults-andremainatahigherlevel

　　laterinthemorning.Measuringthehormoneinthesalivaisagoodwaytoshowthatmostteenshave

　　sleepproblems，butchangingschoolschedulesisn’tthebestwaytofixthis.Mostpeoplearguingagainst

　　changingschoolscheduleswouldsaythatitwouldonlycauseteenstostayupandwakeuplater，thus

　　leavingthemwiththesameproblem.

　　Thebiggestproblemschoolswouldcomeacrossfromchangingtheirscheduleswouldbetheafter

　　schoolandjobconflictsstudentsandteacherswouldmeet.“Teachersreportedthatstudentsweremore

　　alert，andresearchshowedthatafterschoolsportsandjobswouldsuffer.Studentsinthatareamighthavebeenabletodealwithlesstimeforjobsandsportssomehow，butsomeofthemhavepracticeandearlierplansthatwouldbecomeconflictedifthischangeweretooccur.Moststudentsrarelyhavetimetoplaya

　　sportanddohomeworkbefore9or10o’clock.Openingschoolslatermayhaveworkedforsomeareas，buttherealityisoftenverydifferent.

　　1．Themeaningoftheunderlinedword“chaotic”inthe1stparagraphiscloseto________.

　　A．positive

　　B．apparent

　　C．negative

　　D．ambiguous

　　2．Mostteenshavesleepproblemsbecause________.

　　A．theyaremoreactivethanchildrenandadults

　　B．schoolworktakesupmostoftheirtime

　　C．theirhormonelevelsarehigherlateratnight

　　D．theyprobablylikestayingupfornoreason

　　3．WhichofthefollowingisTRUEaccordingtothepassage?

　　A．Therearemanyconflictsbetweenstudentsandteachers.

　　B．Someo