Question

question 6
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choose the statement that correctly explains the nitrogen fixation process.
fertilizers are needed to fix nitrogen so it is usable; they allow the nitrogen to be absorbed by plants and passed on to the animals that eat them.
nitrogen is found in dna and amino acids, which are released through animal urination and absorbed by bacteria in the soil.
when animals die, nitrogen is formed by decomposers in the soil; bacteria attach themselves to plant roots and release the nitrogen into the atmosphere.
microorganisms in the roots of certain plants take nitrogen from the air and pass it on to the animals that use it to build dna, proteins, and muscle.

Explanation:

Nitrogen - fixing is done by microorganisms like rhizobia in the roots of leguminous plants. They convert atmospheric nitrogen into a form usable by plants, which is then passed on to animals through the food - chain for building biological molecules. The first option is wrong as fertilizers are not the main agents of nitrogen fixation. The second option describes the nitrogen cycle after nitrogen is already fixed. The third option has an incorrect flow as bacteria in root nodules fix nitrogen from the air, not release it into the air.

Answer:

D. Microorganisms in the roots of certain plants take nitrogen from the air and pass it on to the animals that use it to build DNA, proteins, and muscle.