Answer: those that exists as gases
Explanation:
A nutrient cycling is a process of circulation of vital nutrients through various spheres of earth like atmosphere, biosphere, lithosphere and geosphere.
The nutrients that cycle through atmosphere will be in the form of gases. As atmosphere includes the layer of gases. The aggregate of gases is collectively called as air.
The nutrients like carbon, nitrogen, sulphur, and others can be found as gas in the atmosphere.
