相关usedtobeoneofthemost的文学知识

问题详情：    Thepassengerpigeon(旅鸽)usedtobeoneofthemostcommonbirdsontheearth.Acenturyago,theybecameextinct（灭绝）.ScientistBenNovakisworkingtobringthebirdsback.Here,heexplainstouswhyweshouldbringpas...