Igneous rocks are formed from . sedimentary rocks
fossils and shells
magma
eroded land

magma

Explanation:

actually cooling and solidification of magma

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 : )

are there answer choices to this question? this seems like a question where you have options to choose from.