Whichecological roles is/are played by at least some fungi?

Predation, decomposition

Explanation:

Fungi is very much important for the environment and play an important role in balancing the environment because they play many ecological roles. All fungi are heterotrophs so they depend on others to get their food.

One of the most important roles played by fungi is of decomposers. Most of the fungi are saprophytes and they get their nutrition from dead and decaying organic matter. So by doing this, they help in nutrient cycle and bioremediation.

Some fungi also play the ecological role of predators and prey on amoebas, roundworms, and rotifers, animals, etc. Therefore correct answer is predation and decomposition

most community's take hundreds of years to become stable

sheep is a herbivore animal whereas grasshopper belongs to the class chordates but both of them feed on greens.  

if grasshopper and sheep feeding on a pasture land, i do not think both of them will have any impact on each other. however, the number of the species can make difference. since sheep feed on greens, there is a possibility there left no pasture land for the grasshoppers or they may get extinct.