Research shows that mount everest grows an average of 4 millimeters each year. how many years will it take to grow 720 millimeters?
a. 40
b. 100
c. 180
d. 720

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.

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.