Nitrogen (n2) is o cycled through the environment via the activity of bacteria. o a key component of life, integrated into our bodies directly from the air o now measured at 20.946% by volume in the homosphere. o a product of the radioactive decay of a form of potassium in the crust.

Option (1)

Explanation:

The bacterias plays an important role in the nitrogen cycle. The composition of nitrogen (N₂) in the atmosphere is approximately 78% by volume. The bacterias use this nitrogen to convert into ammonia (NH₃) and they are known as the nitrogen-fixing bacteria. After this, the nitrification process takes place in which the ammonia is transformed into nitrates (NO₃-) by bacteria and these nitrates are absorbed by the plants and are transported to their roots. Lastly, the denitrification process occurs, which converts the nitrate back to the nitrogen. This process takes place by those bacterias which eliminate the nitrates from the soil into the atmosphere forming nitrogen.

Thus, the correct answer is option (1).

a and b because with the other three, they simplify to something else.