Explanation:

Introduction:
Mineral is a component of nitrogenase and nitrate reductase, both of which are enzymes involved in nitrogen metabolism. These enzymes play a crucial role in converting nitrogen gas (N2) from the atmosphere into a usable form for plants and other organisms.

Nitrogenase:
Nitrogenase is an enzyme complex that catalyzes the conversion of atmospheric nitrogen gas (N2) into ammonia (NH3) through a process called nitrogen fixation. This process is essential for the production of nitrogenous compounds such as amino acids and nucleotides. The nitrogenase complex consists of two main components: the MoFe protein and the Fe protein.

Mineral component of nitrogenase:
The mineral component of nitrogenase is molybdenum (Mo). Molybdenum is an essential trace element that functions as a cofactor in the MoFe protein of nitrogenase. It plays a crucial role in the binding and reduction of nitrogen gas. Without molybdenum, the nitrogenase enzyme would not be able to carry out nitrogen fixation effectively.

Nitrate reductase:
Nitrate reductase is another enzyme involved in nitrogen metabolism. It catalyzes the reduction of nitrate (NO3-) to nitrite (NO2-), which is an intermediate step in the conversion of nitrate to ammonia. This process is important for plants to obtain nitrogen from the soil. Nitrate reductase is found in the cytoplasm of plant cells.

Mineral component of nitrate reductase:
The mineral component of nitrate reductase is molybdenum (Mo) as well. Molybdenum functions as a cofactor in the active site of nitrate reductase, allowing for the efficient reduction of nitrate. It plays a crucial role in the transfer of electrons during the conversion of nitrate to nitrite.

Conclusion:
In conclusion, the correct answer is option B, molybdenum (Mo). Molybdenum is the mineral component of both nitrogenase and nitrate reductase enzymes. It acts as a cofactor, facilitating the catalytic activity of these enzymes in nitrogen metabolism. Without molybdenum, nitrogen fixation and the conversion of nitrate to ammonia would be impaired.