Are forests a renewable resource? are they ordinarily used in a renewable way? how can forests be used more sustainably?

Trees are renewable because they can be replenished in a reasonable time frame. It takes too long to 'produce' fossil fuels, so they're not renewable. Thing is, the way we're using trees in most parts of the world is not sustainable. Forests are NOT renewable when they're clearcut or severely reduced. Forests are an ecosystem. When it collapses, species go extinct and don't come back. While we can plant more trees, we can't restore the land to the way it was. Sustainable forestry practices result in a consistent ecosystem which keeps the forest/trees renewable.

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.

if you listed your answers right then i believe your answer is b.