In 3.0 seconds, a wave generator produces 15 pulses that spread over a distance of 45 centimeters. calculate its period.
0.022 s
0.066 s
0.20 s
0.33 s

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 : )

a straight line sloped