• Copper (A) $\rightarrow$ Ascorbic acid oxidase & polyphenol oxidase (II): Copper acts as an essential prosthetic metal ion in cuproenzymes including plastocyanin, cytochrome c oxidase, ascorbic acid oxidase, and polyphenol oxidase involved in terminal redox cascades.
• Iron (B) $\rightarrow$ Catalase & peroxidase (III): Iron functions as the central heme metallic cofactor in hemoprotein enzymes such as catalase and peroxidase that decompose toxic peroxides in plant cells.
• Zinc (C) $\rightarrow$ Carbonic anhydrase & alcohol dehydrogenase (IV): Zinc is mandatory for the catalytic activity of carbonic anhydrase (interconverting $CO_2$ and $HCO_3^-$) and alcohol dehydrogenase in plant root respiration.
• Molybdenum (D) $\rightarrow$ Nitrogenase & nitrate reductase (I): Molybdenum forms the FeMo-cofactor in nitrogenase (catalyzing symbiotic $N_2$ fixation) and the molybdopterin cofactor in nitrate reductase.
• Conclusion: (A)-(II), (B)-(III), (C)-(IV), (D)-(I). (Correct answer: Option 2)

• Umbric Epipedon: In USDA Soil Taxonomy, an umbric epipedon meets all the morphological requirements of a mollic epipedon (thick, dark color with value $\le 3$ and chroma $\le 3$, high organic matter, remains moist $\gt 9$ months per year) except that its base saturation is less than 50% ($NH_4OAc$ method).
• Other Epipedons:
• Mollic: High base saturation ($\ge 50\%$).
• Ochric: Light-colored or thin epipedon lacking diagnostic criteria.
• Melanic: Very dark volcanic epipedon rich in allophane and humus. (Correct answer: Option 3)

• Mechanisms of Plant Nutrient Transport to Root Surfaces (Barber's Concept):
• Nitrogen (Nitrate, $\text{NO}_3^-$): Highly soluble and non-adsorbed; transported almost entirely ($\gt 80\%$) via convective Mass flow $\rightarrow$ (I)
• Phosphorus (Orthophosphates, $\text{H}_2\text{PO}_4^-$): Strongly adsorbed and precipitated; transported almost exclusively ($\gt 90\%$) via Diffusion $\rightarrow$ (II)
• Potassium ($\text{K}^+$): Readily exchanged on clay edges; transported primarily ($70-80\%$) by Diffusion $\rightarrow$ (III)
• Calcium ($\text{Ca}^{2+}$): Present in high solution concentrations; supplied predominantly through Mass flow and Root interception $\rightarrow$ (IV)
• Systematic Match: (A)-(I), (B)-(II), (C)-(III), (D)-(IV) corresponds to Option 1.

Correct option: (1) (A) - (IN), (B) - (III), (C) - (IV), (D) - @),