Which of the following two cycles are the most closely related in their role in sustaining life?
a. carbon and nitrogen
b. water and nitrogen
c. carbon and oxygen
d. nitrogen and phosphorus

b. water and nitrogen

The biogeochemical cycles move through mainly the biotic and abiotic components of the earth, more elaborately the spheres -biospheres, lithosphere, hydrosphere and atmosphere regions of the ecosystem. These biogeochemical cycles, from its terminology and discernable word morphology- involves the biological, geological and chemical components that make out to complete an exact and purposed cycle. The purpose in these cycles are to maintain balance and to ensure the ongoing process of the living and non-living organisms in the environment. These cycles’ help to living organisms survive and thrive. One popular example is the water cycle. 

No is the answer to the question

The correct answer is "atomic weight".