Which cycle includes bacteria taking gas from the atmosphere and converting it into a material that plants can absorb through root systems?

A. The phosphate cycle

B. The water cycle

C. The nitrogen cycle

D. The oxygen and carbon dioxide cycle

C. The nitrogen cycle.

In this cycle, atmospheric nitrogen is fixed via different nitrogen fixation bacteria to form nitrates and other nitrogen-containing products. These are then taken up by roots of different plants and used to release nitrogen from them and use nitrogen for synthesis of amino acids, which are the basic unit of proteins.

The nitrogen cycle would be the correct answer.