Which are forms of nitrogen that are usable by humans? O A. Phosphorus, nitrates, nodules
O B. Nodules, roots, fertilizer
O C. Ammonia, nitrates, nitrites
D. Oxygen, carbon, water

answer; i believe the answer is hydraulic action;

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds