Guidewords for the word “serpent” may be a.
Serbia and service
c.
Seltzer and Saturday
b.
Seattle and section
d.
Solitude and second
THE CORRECT ONE IS A

A. Serbia and service

Explanation:

A guide word is a word written on top of a page to indicate the first or last word entry on that page. For example in a dictionary, they indicate the alphabetical first and last words on the page.

In this example; the word ' serpent ' note the first three letters to guide you in the words that are on that page;

In this case : Serbia  and Service.

i guess that visual aids present persuasive examples to what you are presenting, some factors would be theme (does it fit with the color, information, what you are presenting), size (can you see it, is it a big enough span of data/information), and overall look of the visual aid.

hope this : )

current flows in a wire