题目内容：
Thedoghasbeenman’sbestfriendforthousandsofyears.Dogsarefriendly,obedientandfaithfulanimals.Manystoriesaretoldofthebraveryandfaithfulnessofdogs.Dogsarealsointelligentanimals,soitiseasytotrainthem.AdognamedBarrysaved40personswhentheywerelostinthesnowontheSaintBernardPassinSwitzerlandabout150yearsago.
Dogsarealsohelpfulinscientificresearch.Theworld’sfirstspace-travelerwasadognamedLaika.Russianscientistssentitupinaman-madeEarthsatellitein1957.Dogshavebeenfilmstars,too.AdogcalledLassiewasthestarinanumberofAmericanfilms.
Dogscanhearandsmellbetterthanman,buttheycannotseesowell.You
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