尔雅 智慧树 mooc

Assumeachangeatthesourceofsoundreducesthewavelengthofasoundwaveinairbyafactorof.Whathappenstoitsfrequency?()AItisunchanged.BItincreasesbyafactorof.CItincreasesbyafactorof.DItdecreasesbyafactorof

  尔雅 智慧树 mooc


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