The correct answer is Equilibrium
The earth's cycle tend to maintain the balance or equilibrium of the earth by maintaining the proper amount of water, nitrogen, carbon, phosphorous on earth. Each of the component of earth's cycle is equally important because they support life on earth.They are basis of life as carbon is found in abundant amount in all the life forms. Phosphorous, nitrogen and water is equally important in the human beings as well as in plants and animals.
Hence, they maintain the equilibrium of earth.