Which graph shows the presence of nitrogen-fixing bacteria in the soil

Graph 2 represents the presence of nitrogen-fixing bacteria in the soil.

This is because in this graph the concentration of atmospheric nitrogen (N2) is lower and the concentration of ammonium (NH4) is higher. The nitrogen-fixing bacteria converts or fixes atmospheric nitrogen that can't be absorbed by the plants into ammonium or nitrates which can be absorbed by the plants and make necessary amino acids for the body so we can conclude that graph 2 indicates the presence of nitrogen-fixing bacteria in the soil.

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the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.

the tricuspid valve is present between right atrium and right ventricle