Black Friday: lifetime access is on a special offer in the app, until November 30. Black Friday: special offer on lifetime access, until November 30. Download
새의 울대는 그들의 소리를 만드는 데 중요한 역할을 합니다.saeui uldaeneun geudeului sorireul mandeuneun de jungyohan yeokhal-eul hamnida.The syrinx of birds plays an important role in producing their sounds.