Bacteria from the soil absorb nitrogen from the air and convert it into ammonium. this is an example of
the hydrologic cycle
nitrogen fixation
assimilation
carbon cycle

Nitrogen Fixation

Explanation:

The bacteria that is present in the soil converts the atmospheric nitrogen into the form that can be used by the plants.

The form of nitrogen that is present in the atmosphere is not used by the plants has to be first converted in the form which can be used by the plants.

These bacteria are found in the roots of the legumes which gets food from the roots of the plant and fixes nitrogen for the plant.

Hence, the correct answer is option B

a = executive branch; b = judicial branch