The term that describes the optical trick of swelling columns at midpoint, which was used in the design of the Parthenon is entasis.
If you take a look at the ancient Greek columns, you will see that they are a bit wider in the middle - so the column is not completely straight, but rather swells up in the middle so as to "correct the visual illusion of concavity." It was often used by artists in the ancient Greek times.
A composer writes a musical manuscript called a score
The answer is (d.) choose only the visuals that are easily understood.
The main purpose of the visual aids is to help improve the understanding of the audience to the presentation. It clarifies and reinforce the key points of the topic. So it's important to choose the appropriate visual that could help the presentation easily understood.
