How are the carbon, oxygen, and nitrogen cycles vital to sustaining life on earth? . a.. carbon, oxygen, and nitrogen are vital components of life on earth.. b.. the carbon, oxygen, and nitrogen cycles allow vital elements to return to usable form by organisms.. c.. the carbon, oxygen, and nitrogen cycles are an important interface between biotic and abiotic factors.. d.. all of the above are reasons the carbon, oxygen, and nitrogen cycles are vital to life on earth