How does source credibility affect persuasive impact, and when is it most influential?

How does source credibility affect persuasive impact, and when is it most influential?

• A. High credibility increases impact only when issues are simple.
• B. Credibility matters equally for all audiences, regardless of motivation.
• C. High credibility increases impact, especially when the recipient is motivated and uses central processing; credibility also matters in ambiguous or complex issues.
• D. Credibility has no impact on attitudes.

Answer: (C)