Why Are Biogeochemical Cycles Crucial to the Maintenance of Our

Why are biogeochemical cycles crucial to the maintenance of our planet's ecosystems? (Select all that apply)

A) unusable forms of elements such as carbon, sulfur and nitrogen are converted to forms usable by living organisms.
B) decomposition of dead organisms releases minerals back into the ecosystem for reuse by other organisms.
C) breakdown of waste materials from living organisms puts bacteria back into the environment.
D) these cycles prevent pollutants from spreading throughout the biosphere.