阅读下面短文，根据短文内容，在短文后面小题中句子空白处填入适当的词语或句子。
Weknowthatmanyanimalsdonotstayinoneplace．Birdsfishandotheranimalsmovefromoneplacetoanotherplaceatacertaintime．Theymovefordifferentreasons：mostofthemmovetofindfoodmoreeasilybutothersmovetogetawayfromplacesthataretoocrowded．
Whencoldweathercomesmanybirdsmovetowarmerplacestofindfood．Somefishesgivebirthinwarmwaterandmovetocoldwatertofeed．Themostfamousmigrationisprobablythemigrationoffishwhichiscalled“salmon”(鲑鱼)．Thisfishisborninfreshwaterbutittravelsmanymilestosaltwater．Thereitspendsitslife．Whenitisolditreturnstoitsbirthplaceinfreshwater．Thenitgivesbirthanddies．InnorthernEuropethereisakindofmouse．Theyleavetheirmountainhomeswhentheybecometoocrowded．Theymovedowntothelowland．Sometimestheymoveallthewaytotheseasideandmanyofthemarekilledwhentheyfallintothesea．
Recentlyscientistshavestudiedthemigrationofakindoflobster(龙虾)．Everyyearwhentheseasonofthebadweatherarrivesthelobstersgetintoalonglineandstarttowalkacrosstheflooroftheocean．Nobodyknowswhytheydothisandnobodyknowswheretheygo．Sosometimesweknowwhyhumansandanimalsmovefromoneplacetoanotherplacebutatothertimeswedon’t．Maybelivingthingsjustliketotravel．
1．Thereasonformostoftheanimalstomoveis________．
2．Findthewordinthepassagewhichmeans“themovementfromoneplacetoanotherofalargegroupofanimals”andwriteitdownhere：________．
3．Theunderlinedword“There”inthesecondparagraphrefersto(指的是)________．
4．Thesalmoncomesbacktoitsbirthplaceinorderto________．
5．Thelobstersbegintomovetoanotherplacewhen________．
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