If one body is positively charged and another body is negatively charged, free electrons tend to
a. remain in the positively charged body.
b. move from the negatively charged body to the positively charged body.
c. remain in the negatively charged body.
d. move from the positively charged body to the negatively charged body.

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 : )

okay i have so many questions. but the big one here is: um wt..f is this mess? ?