What is the carbon cycle?

Nitrogen?

Phosphorus?

The series of processes by which carbon compounds are interconverted in the environment, chiefly involving the incorporation of carbon dioxide into living tissue by photosynthesis and its return to the atmosphere through respiration, the decay of dead organisms, and the burning of fossil fuels ...

Clues it's found in the periodic table search it on google just put periodic table of natural elements and you'll see those that you've listed