Final answer:
Volume, articulation, and rate are essential to a speaker's credibility, along with clear gestures, expressions, and established credibility.
Step-by-step explanation:
Important aspects to a speaker's credibility include volume, articulation, rate, and pitch. Effective speakers must regulate their volume to ensure they are heard clearly without being too loud or too soft. Articulation needs to be clear to avoid misunderstandings and to keep the audience engaged. The rate must be managed to maintain a natural and understandable pace, while also utilizing changes in rate to emphasize points. Gestures, expressions, and credibility also play vital roles in speech delivery.