题目内容：
根据下面内容，回答题 AnationalsurveyshowedthatmanyofAmerica'spublicschoolteachersspendtheirowntimeexpandingtheknowledgeandskills.
Professionaltrainingisawayoflifeformanyteachers.Someevengotosummerschoolstolearnnewskillsandkeepupwithadvancesintechnology.
Theaverageteacherhas25yearsofclassroomexperienceandmorethanhalfholdamaster'sdegree.Nearly23percentbeganfull-timeteachingwithinthepastfiveyears.Thisstatisticshouldcausesomeconcernsbecauseitmeansalargenumberofteachersarereachingtheretirementage.Ifthistrendisnotrecognized,atsomepointthiswillresultinanexperiencegap.
Withsalariesbasedonfewerhoursandnoovertime,thecomplaintsoftheteachersbecomemoreunderstandable.Manyoutsidersfeelthatthelongsummervacationsjustifylowerpayscales,butinreality,manyteachersspendagoodpartoftheirvacationhoningtheirskillsfortheupcomingyear,Facingaclassroomunpreparedistougherontheteacherthanonstudents.
Evenwithallofthese,threefifthsofteachers(60percent)saidtheywouldbecometeachersagain.However,thereweremanywhosaidtheywouldnotchooseteachingasacareeriftheycouldstartoveragain.
Forthefirsttime,thesurveysoughtthereasonsforteachersleavingtheprofession.Themostoftencitedreason(37percent)forabandoningtheirtrainingandprofessionalexperiencewaslowsalaries.Minorityteachers(50percent),maleteachers(43percent),andteachersunder30(47percent)weremostlikelytoclaimlowpayasthereasontheywillnotstayinteaching.
WhatdoweknowaboutAmericanpublicschoolteachersfromthepassage? A．Theyeitherhaveamaster'sdegreeorenoughexperience.
B．Theyspendtimeexpandingtheirknowledgeandskills.
C．Theyareaskedtokeepupwithadvancedtechnology.
D．Theymustgotosummerschooltolearnnewskills.
参考答案：
答案解析：