Answer:
The option A is the correct option. The fungi share a mutualistic association with the trees.
Step-by-step explanation:
Mutualism or interspecific cooperation is the way two organisms of different species exist in a relationship in which each individual fitness benefits from the activity of the other. And in this case, both plant and fungi are benefited by each other. The plant provides food and habitat for the living of fungi and fungi, in turn, decompose dead organic matter to provide simple compounds to plants.
While in commensalism only one either plant or fungi can be benefited. And it is also not a parasitic interaction.