It would be B, contour plowing
The water cycle is a parameter of the hydrosphere that always remains constant. Life on Earth and its sustenance is possible because of this cycle. The continuous evaporation, condensation, and precipitation of water provides for the many processes involved in Earth's natural surroundings. Without the water cycle, life would cease to exist.
The correct answer is (d.) proteins. Higher organisms use nitrogen to make their protein. Food that is containing protein also involves nitrogen in it. Protein also has amino acids that contain nitrogen in it which is a necessary essential nutrient for the body.
