Themaincharacteristi的精选

问题详情：请认真阅读下面短文,并根据短文内容回答问题Themaincharacteristicofabirdisfeathers.Nootheranimalhasfeathers.Otherimportantfeaturesforbirdsarewingsandhollowbones.Birdsflybyflappingtheirwingsandusi...