Which of the following statements about speakers’ credibility is true?

A、Aspeaker’scredibilityisbasedonherorhisreputationratherthanonwhathappensduringaspeech.;
B、Credibilityreferstothespeaker’struecharacterandcompetence,notmerelytotheaudience’sperceptionofthespeaker.;
C、Aspeaker’scredibilityisaffectedbyalmosteveryaspectofthespeechexceptdelivery.;
D、Thesamespeakercanhavehighcredibilityforoneaudienceandlowcredibilityforanotheraudience.