Nitrogen is an important element that is vital for organisms to perform various functions. In animals, it is available by the plants they eat because of the nitrogen cycle. Thus, option B is correct.
The nitrogen cycle is the part of the biogeochemical cycle where the nitrogen is converted and fixed into a usable form for the organisms. The cycle continues in the atmosphere, lithosphere, and hydrosphere.
The cycle comprises a various process that includes the fixation of nitrogen followed by nitrification, denitrification, and then decay. During the process, the nitrogen moves through the biotic and abiotic factors.
The cycle converts the nitrogen from the atmosphere into usable forms like ammonia that are taken by the plant roots to make food. The plants are consumed by animals and hence pass the nitrogen compound.
Therefore, the plants in the diet provide the essential nitrogen to the animals.
Learn more about the nitrogen cycle here:
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