Which of the Following Processes Directly Require the Activity of Microorganisms

Which of the following processes directly require the activity of microorganisms?

A) release of organic carbon into the environment from animal and plant remains
B) absorption of sulfate from the environment by green plants
C) release of organic nitrogen into the environment by dead plants and animals
D) conversion of organic phosphorus in animal and plant remains into inorganic phosphorus
E) All of the above require microbial activity.