Water consumption has increased by how much over the last century?

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 : )

d. air pressure decreases as altitude increases.

well clustered together.

points close on a scatter diagram