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Among the choices the answer letter C which is "<span>the left and right sides"</span>
Answer:
C.
Explanation:
Nitrogen fixation is a process by which molecular nitrogen in the air is converted into ammonia or related nitrogenous compounds in soil. Atmospheric nitrogen is molecular dinitrogen, a relatively nonreactive molecule that is metabolically useless to all but a few microorganisms.
Lymphocyte is one of body immune cells that works by fighting bacteria. To distinguish foreign material to body material, lymphocyte can detect a series of protein called antigen. Most antigen is represented by macrophages. In response to the antigen, lymphocyte might produce an antibody which will bind to the antigen.
Answer: Antigen
