题目内容：
根据下面内容，回答题 Weknowthatmanyanimalsdonotstayinoneplace.Birds,fishandotheranimalsmovefromoneplacetoanotheratacertaintime.Theymovefordifferentreasons;mostofthemmovetofindfoodmoreeasily,butothersmovetogetawayfromplacethataretoocrowded.
Whencoldweathercomes,manybirdsmovetowarmerplacestofindfood.Somefishesgivebirthinwarmwaterandmovetocoldwatertofeed.Themostfamousmigrationisprobablythemigrationofthefish,whichiscalled"salmon".Thisfishisborninfreshwaterbutittravelsmanymilestosaltwater.Thereitspendsitslife.Whenitiscold,itreturnstoitsbirthplaceinfreshwater.Thenitgivesbirthanddiesthere.InnorthernEurope,thereisakindofmouse.Theyleavetheirmountainhomeswhentheybecometoocrowded.Theymovedowntothelowland.Sometimestheymoveallthewaytotheseaside,andmanyofthemarekilledwhentheyfallintothesea.
Recently,scientistshavestudiedthemigrationofakindoflobster.Everyyear,whentheseasonofbadweatherarrives,thelobstersgetintoalongtimeandstarttowalkacrosstheflooroftheocean.Nobodyknowswhytheydothis,andnobodyknowswheretheygo.
So,sometimesweknowwhyhumansandanimalsmovefromoneplacetoanother,butat
othertimeswedon't.Maybelivingthingsjustliketotravel.
Themajorityofanimalsmigratefor__________ A．place
B．safety
C．food
D．warmth
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答案解析：