Final answer:
Nitrogen fixation is the process of converting atmospheric nitrogen into organic molecules like ammonia, enabling plant utilization for essential compounds such as nucleotides and proteins. Option B is correct.
Step-by-step explanation:
The process whereby nitrogen is brought into organic molecules is called nitrogen fixation. During this biological process, certain bacteria, including those that live in symbiotic relationships with leguminous plants, convert atmospheric nitrogen gas (N2) into a form that plants can use, typically ammonia (NH3). This is crucial for the synthesis of essential organic compounds like nucleotides and proteins. Nitrogen fixation is part of the nitrogen cycle, which is essential for agricultural production and maintaining the ecosystem's balance.