Which step is not involved in the carbon cycle?

Which of the following processes is not a step involved in the water cycle operating in nature?

$(i)$ In what form do plants utilize nitrogen?
$(ii)$ Why do they need nitrogen?

With the help of a labelled diagram,show the carbon cycle in nature. Describe the two ways in which carbon dioxide is fixed in the environment.

The nitrogen molecules present in air can be converted into nitrates and nitrites by:

What are the two ways in which carbon dioxide is fixed in the environment?