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Fungus growing inside an anthill
Fungus growing on the leaves of plants
Fungus used as food for human consumption
Fungus used to make medications for humans
Well if the fungus is benefitting the leaves, then it would be the second option. I am pretty sure that fungus growing inside an anthill is either hurting the ants or neither of them benefit, making this option incorrect. Fungus used as food for human consumption is not mutually beneficial because the fungus is… well being eaten. Finally, fungus used to make medications for humans is beneficial for the humans, but probably not for the fungus as it is probably dying. In my opinion, this question could use some more information to properly answer it, but given the information above, I would say the second option is the best. Hope this helped a bit:)