wAlt whitmAn wAs A pionEEring FigurE oF AmEriCAn poEtry. his innovAtion, First oF All, liEs in his usE oF ______, poEtry without A FixED rEgulAr rhymE sChEmE.
A．BlAnk vErsE
B．hEroiC CouplEt
C．FrEE vErsE
D．iAmBiC pEntAmEtEr