What is the name of the cycle through which nitrogen gas is converted into forms that plants can use?

The correct answer is the Nitrogen Cycle. This cycle is a crucial ecological process that describes how nitrogen gas (N₂) from the atmosphere is transformed into various forms of nitrogen that plants can readily absorb and utilize for growth.

The cycle begins with nitrogen fixation, where certain bacteria in the soil or in symbiosis with plants convert atmospheric nitrogen into ammonia (NH₃). This ammonia can then be further processed by other bacteria into nitrites (NO₂⁻) and nitrates (NO₃⁻), which are forms of nitrogen that are easily taken up by plant roots. Once plants absorb these nitrates, they use nitrogen to synthesize essential biomolecules like proteins and nucleic acids.

After plants are consumed by animals, nitrogen is returned to the soil through waste products and when organisms decompose, eventually re-entering the nitrogen cycle. This continuous cycle ensures that nitrogen is available throughout the ecosystem, supporting plant growth and sustaining food webs.

In contrast, the other cycles listed—such as the Carbon Cycle, Water Cycle, and Phosphorus Cycle—deal with the movement and transformation of carbon, water, and phosphorus, respectively, and do not play a direct role in converting nitrogen gas into usable forms for plants. Each of