Answer:
C. To support a speaker's point by providing evidence or clarity.
Step-by-step explanation:
Visual aids, such as photographs, videos, diagrams, graphs, charts, etc. have the ability to enhance a speech by providing evidence or clarifying a specific point or showing data in a way that is easily comprehendable and/or comparable (i.e. a line graph comparing two sets of data, or a pie chart showing the composition of the data).