这个得看具体题目而定

　　我告诉你它们的区别,你自己想想好了

　　区别：

　　关系代词用that（不用which）的情况：

　　1.先行词是all,anything,everything,nothing等,关系代词应用that

　　That'sallthathetoldme.

　　2.先行词前有theonly,thesame,thevery或no,little,much,any,every,all等修饰时,关系代词应用that

　　SheistheonlypersonthatIknowinthiscompany.

　　3.先行词前有序数词或形容词最高级修饰时,关系代词常用that

　　ThefirstthingthatIwanttodoistotakeitaway.

　　4.当先行词同时含有"人"或"物"时,关系代词应用that

　　5.在固定结构thesame...that...;so...that...;such...that...以及itis/was...that...的强调句型中,要用that

　　Thisisthesameparkthatweoncevisited.

　　6.如主句以therebe开头时,关系代词应用that

　　Thereisaroomthathastwowindows.

　　关系代词用which（不用that）的情况：

　　1.非限制性定语从句中关系代词一般要用which

　　Shewonthecompetition,whichmadethewholefamilyveryhappy.

　　2.关系代词前如有介词,关系代词须用which;如把介词移至句末,可用that(或省略)

　　There’sonlyoneproblemaboutwhichtheydisagree.

　　Thisisthekey(that)shewaslookingfor.

　　3.如果先行词是that,关系代词应用which

　　Iknowthatwhichyoutoldme.

　　4.如先行词和定语从句之间被其它较长的成分分隔,常用which

　　LarrytoldherthestoryoftheyoungairmanwhichInarratedatthebeginningofthisbook.(先行词为story)

　　5.在"those+复数形式的名词"结构中,其后的关系代词多用which

　　Ashopshouldkeepastockofthosegoodswhichsellbest.

　　6.一个句子中如有两个定语从句,第一个定语从句用了关系代词that,第二个从句中的关系代词宜用which;但在平行结构中,应重复同一个关系代词

　　Thisisthebookthatyouboughtwhichyouhavelost.

　　Ihaveahousewhichislocatedonthehillside,whichfacesthesouth.

　　此外,that还可引导同位语从句,which不能

　　Ihaveheardthenewsthattheyhadwonthegame.