• Thermodynamic Basis of DNA Stability:
• Base pairing via hydrogen bonds (2 between A-T, 3 between G-C) provides structural fidelity, sequence specificity, and precise alignment of keto/amino tautomers.
• When single strands hybridize into an ordered double helix, conformational entropy of the polynucleotide backbone decreases ($\Delta S_{\text{chains}} \lt 0$). However, the release of ordered water molecules from non-polar surfaces during hydrophobic base stacking provides a favorable net entropic gain ($\Delta S_{\text{solvent}} \gt 0$).
• False Statement: Stating simply that hydrogen bonding "decreases the entropy" is false or misleading; the net thermodynamic stability ($\Delta G = \Delta H - T\Delta S$) is primarily driven by favorable negative enthalpy (hydrogen bonding and van der Waals stacking) and hydrophobic effect.

Correct option: (3) Decreases the entropy