PeriodThree介词+关系代词引导定语从句时，__________和_________不能用于介词后，能用于介词+关系代词引导定语从句的代词只有__________（代指事物）和___________（代指人），且关系词不可___________。e.g1.Themanisafamousrunner.Youtalkedtohimjustnow.Themantowhomyoutalkjustnowisafamousrunner.2.Thechairismadeofwood.Heissittingonitnow._________________________________________________________3.Heisalibraryassistant.Iborrowedsomebooksfromhim._________________________________________________________介词的选择依据：①介词与定语从句的先行词是一种习惯性的搭配。Thefarm_______whichIonceworkedhastakenanewlook.②介词与从句中动词是一种习惯性搭配。Whoistheman_______whomourteacherisshakinghands?③介词与定语从句中的形容词一起构成一种习惯性的短语。Oursisabeautifulcountry,_______whichwearegreatlyproud.④表示“所有格”或“整体与部分关系”时，用介词of.Thereareover3,000workers,eightypercent______whomarewomen.备注：当关系代词在从句中作介词宾语时，介词可以提前（which和whom前）亦可放于原来的位置，但在含有介词的固定词语中，介词不能提前如lookfor,lookafter,takecareof。e.g.Heisthestudentwhotheteachersarelookingfor.Practice：一、把下列每对句子合并成含有定语从句的主从复合句：1.Theserviceshouldbeimproved.Thestudentscomplainalotaboutit.2.Theypassedafactory.Atthebackofthefactorytherewerericefields.3.Thesoldierrantothebuilding.Onthetopofitflewaflag.4.Intheeveningtheyarrivedatahill.Atthefootofthehilltherewasatemple.5.Shecameintoabigroom.Inthemiddleofitstoodalargetable.二、选择适当的介词+关系代词，把下列句子补充完整1.Theperson_____________IspokejustnowisthemanagerthatItoldyouabout.2.Thisistheboy____________wehavetosay“Thankyou”.3.IhavenotmetMr.Wang,theson____________ismyEnglishteacher.4.Thepencil____________hewaswritingbroke.5.Thatwastheperiod____________mycousinstayedinmyhome.6.Thebuilding______________weheldthemeetinglastyearhasbeenpulleddown.7.Thetwothings_________________MarxwasnotsurewerethegrammarandsomeoftheidiomsofEnglish.8.Thefamily_______________IstayedinRomeiscomingtoEnglandsoon.9.Hehaswrittenabook,thename____________Ihavecompletelyforgotten.10.Itisafamilyofeightchildren,all________________arestudyingmusic.11.Canyousuggestatime_____________itwillbeconvenienttomeet.12.Thetown,______________theycame,wasinthenorthofthepro