- 問題詳情:Astronautshavealreadyvisitedthemoonandlivedonspacestations.They'veneverbeentoanotherplanet,buttheymightvisitMarssoon.Theastronautswillspendaboutsixmonthstravelingtotheplanet,thenabouttwoyearsontheplanetandaboutsixmonthstravelingbacktotheeart...
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