Answer:
13: d
14: d
Explanation:
Filteration is useful when the things you are trying to separate are in different states - i.e an insoluble solid from a liquid.
Homogeneous mixtures are made up of substances in the same state (e.g multiple gases in air), so couldn't easily be separated in filtration.
Solutions have solutes dissolved in them, so they could also not be separated by filtration (e.g salt water or alcohol solution).
Elements are made up of one thing, and depending on the element it would depend on how you separated it. You could have two gases, like hydrogen and helium, which would be hard to separate by filtration!
That leaves heterogeneous mixtures, which are in different states to each other, so this would be an appropriate way to separate them.
Hope this helps! Let me know if you have any questions :)
