Part A: In the Nitrogen Cycle, how does unusable atmospheric nitrogen become usable in the soil? Part B: In the Carbon Cycle, how do humans influence the greenhouse affect?

Explanation:

The atmospheric nitrogen (N2) is transfered into Amoniom ion (NH4+) by a special bacteria which lives in soil. This process is called Nitrogen fixation. The Amoniom ion is absorbed by plant.

When human is breathing CO2 (Carbon dioxide) is coming out to air. CO2 is one of the gasses that has a big influence on green house affect.

Besides، burning fossil fuels by humans is also another example of human effects on green house affect.

the correct answer is c   with the systems

the missing space is phylum