Themaincharacteristi的精選

問題詳情：請認真閱讀下面短文,並根據短文內容回答問題Themaincharacteristicofabirdisfeathers.Nootheranimalhasfeathers.Otherimportantfeaturesforbirdsarewingsandhollowbones.Birdsflybyflappingtheirwingsandusi...