According to the (1) , there is a fixed amount of nitrogen on Earth. Nitrogen that exists in the air is fixed by (2) in root nodules. This allows it to exist in the soil. (3). then use the nitrogen to make proteins and other complex compounds. When animals eat the plants, the nitrogen is then transferred to their bodies. When these organisms die, the nitrogen is broken down by (4) and returned to the air by bacteria. (1) Law of Conservation of Mass
Law of Conservation of Energy

(2) plant
bacteria
fungi

(3) animal
plant
bacteria

(4) fungi
animal
plant

these are the choices thank you