The correct answer is C. In the plaque assay for bacteriophages, the plaque is a clear zone caused by a zone of lysis.
Explanation:
The plaque assay is an approach used for titering bacteriophage stocks or determining the quantity of infectious virus in a sample. Plaques are visualized if you spot the phage on a lawn of growing compatible bacteria. Each plaque indicates an initial infection with one phage followed by lysis of neighboring bacteria in the lawn. Only viruses that cause visible damage of cells can be assayed in this way. The plaque assay is used to determine viral titer as plaque-forming units per ml so that known amounts of virus can be used to infect cells during subsequent work.
In the plaque assay for bacteriophages, the plaque is a clear zone caused by a zone of lysis.
The nitrogen cycle is a natural process that adds nitrogen to the soil. However, the use of fertilizers has increased the amount of usable nitrogen in the soil. The extra nitrogen seems appealing from the agricultural viewpoint that more nutrients in the soil means higher yield crops.
