The correct answer is Fungus is Limiting factor and biotic factor.
The Fungus on the the oak trees act as limiting factor because the fungus causes disease in the oak trees and leads to decrease in the number of producers(oak trees).
The decrease in the number of producer will decrease the food for the consumers.
In this way it is a limiting factor.
As the fungus is the living factor of the ecosystem hence considered as biotic factor.
