To the reader of a text better understand what something looks like, the author could include ?

a visual.
a chart.
a heading.
a subheading.

A visual.

Explanation:

Using a visual in the text is helpful to understand the meaning or to picturise what the author wants to convey.

This concept of using a visual in the text is often called visual text. A visual text is used to communicate the message using an image than words. Some examples of visual text are photographs, illustrations, cartoons, etc.

So, in order to help the readers better understand what something resembles, an author can include a visual in his/her text.

So, the correct answer is visual.

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