<span>The nitrogen cycle could not exist without first nitrogen. The cycle is about this specific element which goes to show that if this element is not present then, there will not be any nitrogen cycle. Also, an important factor for the cycle is the presence of the bacteria and other microorganism which are needed for the fixation. </span>
<span>A sustainable system refers to producing less or probably non-existent debris that are caused by the production of a particular material (i.e. produce, energy). This is a sustainable form of production of coupling algae growth and fish farming because you no longer need the supply of fish feed from other sources that are made artificially but rather, you are using the available algae growth that you are culturing. Farm fishing alone is non-renewable because this produces much waste that can directly harm the environment.<span>
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C
in the first paragraph a fact is challenged
and the second one provides an example
The answer to your question is c
