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

Following two cycles are the most closely related in their role in sustaining life  are carbon and oxygen 
 all living thing need carbon because  to perform properly. because carbon is found everywhere from the ocean to the sky to rocks. The movement of carbon is known as the carbon cycle

Oxygen is very important to living organisms. The oxygen cycle  have following steps. The oxygen cycle is  interconnected with the carbon cycle because carbon and oxygen are  combined in a molecule. The oxygen cycle  consists of animals who inhale oxygen from the atmosphere and plants that release oxygen in the atmosphere.