What phenomenon results from the runoff of fertilizers from agricultural and residential areas causing the aquatic algae in bodies of water to grow prolifically?

Eutrophication is what the phenomenon called.  Eutrophication This process induces growth of plants and algae and due to the biomass load, may result in oxygen depletion of the water body. It is a choking of rivers, lakes and other waterways by excess algae growth which has been stimulated by fertilizers or sewage.

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.

c: warm water flows from the western tropical pacific toward south america. that should be the right answer! hope it .