Which two layers make up the earth's upper mantle?
question 1 options:
inner core
lithosphere
outer core
asthenosphere

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 : )

.) the observation by semmelweis that more mothers died of childbed fever when their doctors also worked in the morgue

d) physical means can be used to separate the components of air.