Haveyoueverwonderedwhybirdssing?Maybeyouthoughtthatthe...
問題詳情： Haveyoueverwonderedwhybirdssing?Maybeyouthoughtthattheywerejusthappy.Afterall,youprobablysingorwhistlewhenyouarehappy. Somescientistsbelievethatbirdsdosingsomeofthetimejustbecausetheyarehap...