Visual aids are the items which can be illustrated and seen by the audience. This includes presentations, graphs, drawings, charts, etc.
When a speaker uses visual aids in his speech in a right manner, it clarifies the point to the audience.
When used a correct manner, it also enhance the credibility of the speaker. Credibility of the speaker is enhanced using visual aids because this audience will know that the speaker knows much about the topic he is speaking about. And this creates confidence also in the speaker.
Virgil represents reason and wisdom. He sometimes cannot accept Dante's sympathy and informs him that the punishment introduced to the residents of Hell is part of God's plan. He explains all the functions of Hell to Dante. Virgil can be seen as a geographical and spiritual guide.
This short description of character analysis shows that the correct answer is C.
