现要配制pH=4.5的缓冲溶液，最理想的缓冲对是 ()

已知HAc的pKa=4.75，当溶液的pH=7.25时溶液中的主要型体是（）

已知NH3·H2O的pKb=4.74，计算0.10mol∙L-1NH4Cl溶液的pH（）

将以下数修约为4位有效数字正确的是（）

4．通过Post方法提交数据，会将所有数据显示在URL地址的后面。（）

4.不能在不同用户之间共享数据的方法是（）（A）通过cookie（B）利用文件系统（C）利用数据库（D）通过ServletContext对象

4．母は背が高いですが、父（　）低いです。

4.ThenationalflagofthePeople'sRepublicofChinaisredincolor,rectangularinshape,withfivestars.

Althoughmanyofusmayfeelair-conditionersbringrelieffromhot,humidorpollutedoutsideair,theyposemanypotentialhealthhazards.Muchresearchhaslookedathowthemovementofairinsideaclosedenvironment---suchasanofficebuilding---canspreaddiseaseorexposepeopleinthebuildingtoharmfulchemicals.OneofthemorewidelypublicizeddangersisthatofLegionnaire’sdisease,whichwasfirstrecognizedinthe1970s.Thiswasfoundtohaveaffectedpeopleinbuildingswithair-conditioningsystemsinwhichwarmairpumpedoutofthesystem’coolingtowerswassomehowsuckedbackintotheairintake(通风口),inmostcasesduetopoordesign.Thewarmair,filledwithbacteria,wascombinedwithcooled,conditionedairandwasthencirculatedaroundvariouspartsofthebuilding.Studiesshowedthatevenpeopleoutsidesuchbuildingswereatriskiftheywalkedpastairexhaustpipes.Largeair-conditioningsystemsaddwatertotheairtheycirculatebymeansofhumidifiers(湿度调节器).Inoldersystems,thewaterusedforthisprocessiskeptinspecialreservoirs,thebottomsofwhichprovidebreedinggroundsforbacteriawhichcanfindtheirwayintotheventilation(通风)system.Therisktohumanhealthfromthissituationhasbeenhighlightedbythefactthattheimmunesystems(免疫系统)ofapproximatelyhalfofworkersinair-conditionedofficebuildingshavedevelopedtheabilitytofightofftheorganismsfoundatthebottomofsystemreservoirs.Butchemicalscalled“biocides”areaddedtoreservoirstomakethemgerm-free,andtheyaredangerousintheirownrightinsufficientquantities,astheyoftencontaincompoundsstronglylinkedtocancers.Finally,itshouldbepointedoutthattheartificialclimaticenvironmentcreatedbyair-conditionerscanalsoaffectus.Inanaturalenvironment,whetherindoororoutdoor,therearesmallvariationsintemperatureandhumidity.Indeed,thehumanbodyhaslongbeenaccustomedtothesenormalchanges.Inanair-conditionedlivingorworkingenvironment,however,bodytemperaturesremainwellunder37℃,ournormaltemperature.Thisleadstoaweakenedimmunesystemandthusgreaterexposuretodiseasessuchascoldsandflu.4.Theauthormostprobablywantsthereaderstotreatbiocideswithanattitudeof_.

4.Chancesareyou’veactuallyseenthisplace.SongdoappearsinthemostfamousmusicvideoevertocomeoutofSouthKorea.

最迟到4岁，男孩和女孩就已经分别确认了他们的性别认同(genderidentity)。

胸外心脏按压深度:成人4-5厘米，儿童3厘米，婴幼儿2厘米.

当一页内容已满，而文档文字仍然继续被输入，Word将插入()。

字号中阿拉伯字号越大，表示字符越（）中文字号越小，表示字符越（）。

艺术字对象实际上是：（）