The element which helps in biological nitrogen fixation is:

Correct option is D

✅ (d) Mo (Molybdenum): • Molybdenum is essential for the enzyme nitrogenase, which facilitates biological nitrogen fixation in legumes. • It acts as a cofactor in the enzyme complex and is vital for nodule function and efficiency.
❌ (a) Magnesium: • Important in chlorophyll but not for nitrogen fixation.
❌ (b) Manganese: • Involved in photosynthesis and enzyme activation, not specifically for nitrogen fixation.
❌ (c) Zinc: • Needed for enzyme activity but not directly linked with nitrogenase.