Which of the Following Statements Is Correct About Biogeochemical Cycling

Which of the following statements is correct about biogeochemical cycling?

A) Phosphorus is the limiting nutrient that most widely affects biomass production.
B) The phosphorus cycle involves the weathering of rocks.
C) The carbon cycle has maintained a constant atmospheric concentration of carbon dioxide for the past million years.
D) The nitrogen cycle involves movement of diatomic nitrogen between the biotic and abiotic components of the ecosystem.