The majority of a forensic scientist's time is spent

Investigating physical evidence.

Explanation:

Forensic scientists pay a lot of time to analyze the evidences. The analysis process is time consuming, requires labor, skill, expertise and technology. The analysis process may take few hours to many days depending upon the obtained evidences. They analyze the results and frame them in expert testimony in such a way so that these can be used for the purpose of conviction of the culprit.  

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.

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