When sunlight strikes earth, approximately
a. 30% is reflected back into space
b. 70% is reflected back into space
c. 50% is absorbed by the atmosphere
d. 80% is absorbed by land and oceans

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 : )