Why does the Earth orbit the sun? Why doesn't it just fly out into space? A. electromagnetic energy
B. magnetic field
C. the sun is a star
D. gravity

d

Explanation:

Just as the Moon orbits the Earth because of the pull of Earth's gravity, the Earth orbits the Sun because of the pull of the Sun's gravity.

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.

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link: