• Statement (I) is True: Active absorption of water occurs through the metabolic and osmotic activity of root cortical and endodermal cells, generating root pressure ($0.1\text{ to }0.2\text{ MPa}$).
• Statement (II) is False: Active absorption operates independently of transpiration and is most prominent under low transpiration conditions (e.g., humid nights leading to guttation). Passive absorption, which accounts for $\gt 95\%$ of water uptake, is directly driven by the transpirational pull generated in leaves.
• Conclusion: Statement (I) is true but Statement (II) is false.

Correct option: (3) Statement (I) is true but Statement (II) is false.

• Diazotroph Definition: Organisms possessing the nif gene cluster capable of reducing atmospheric dinitrogen ($\text{N}_2$) into ammonia ($\text{NH}_3$).
• Escherichia coli is Non-Diazotrophic: Escherichia species naturally lack the nitrogenase enzyme complex and nif operon, and are entirely incapable of biological nitrogen fixation.
• Diazotrophic Genera: Many strains of Pseudomonas (e.g., P. stutzeri), Azotobacter, and related soil proteobacteria harbor functional nif genes and carry out nitrogen fixation.

Correct option: (4) Escherichia

• nif K $

ightarrow$ (II) $\beta$-subunit of MoFe protein: Together with nifD ($\alpha$-subunit), forms the $\alpha_2\beta_2$ tetrameric dinitrogenase catalytic core.

• nif A $

ightarrow$ (IV) Positive regulator of nif and fix genes: Central transcriptional activator that binds upstream activator sequences (UAS) to activate $\sigma^{54}$-dependent nif promoters. - (C) nif S $ ightarrow$ (V) Cysteine desulfurase: Pyridoxal phosphate-dependent enzyme that mobilizes sulfur from L-cysteine for Fe-S cluster core assembly. - (D) nif B $ ightarrow$ (I) FeMo cofactor biosynthesis: Catalyzes the initial assembly of the Fe-S-C core (NifB-co) essential for FeMoco biosynthesis. - (E) nif H $ ightarrow$ (III) Fe protein of nitrogenase: Encodes the $\gamma_2$ homodimeric dinitrogenase reductase that transfers electrons to the MoFe protein.

Correct option: (4) (A) = (I), (B) - (IV), (C) - (V), (0) = (0), (E) =)

• Statement (I) is True: Biological denitrification is the dissimilatory reduction of nitrate ($\text{NO}_3^-$) to nitrite ($\text{NO}_2^-$), nitric oxide ($\text{NO}$), nitrous oxide ($\text{N}_2\text{O}$), and dinitrogen gas ($\text{N}_2$) under anaerobic or waterlogged conditions.
• Statement (II) is True: Facultative anaerobic denitrifying bacteria (e.g., Pseudomonas, Paracoccus) use oxidized nitrogen oxides ($\text{NO}_3^-$) as terminal electron acceptors in anaerobic respiration, coupling electron transport to proton translocation across the membrane to drive ATP synthesis.
• Conclusion: Both Statement (I) and Statement (II) are true.

Correct option: (1) Both Statement (I) and Statement (II) are true.