SDS denatures proteins and binds at a constant ratio of approximately $1.4\text{ g SDS/g protein}$, conferring a uniform negative charge density and identical charge-to-mass ratio. Consequently, separation in the polyacrylamide gel occurs exclusively based on molecular size through the molecular sieving effect of the gel pores.

Stereochemistry and mutarotation of glucose anomers:

• Assertion (A) is true: Pure crystalline $\alpha$-D-glucopyranose has an initial specific rotation of $+112.2^\circ$, while pure $\beta$-D-glucopyranose has an initial rotation of $+18.7^\circ$. When either anomer is dissolved in water, mutarotation spontaneously occurs via reversible open-chain ring opening until both solutions settle at an identical final optical rotation of $+52.7^\circ$.
• Reason (R) is true: The spontaneous mutarotation process converges on an identical thermodynamic equilibrium mixture containing approximately $64\%\;\beta$-anomer, $36\%\;\alpha$-anomer, and $\lt 0.02\%$ open-chain form.
• Because both solutions converge on the exact same molecular composition at equilibrium, their macroscopic optical rotation properties become completely identical, meaning Reason (R) is the direct explanation of Assertion (A).

Fluorophores and their emission spectrum:

• Amino methyl coumarin (AMCA) is excited by UV light and emits bright blue fluorescence ($\sim 440\text{ to }450\text{ nm}$), matching (IV).
• Rhodamine fluorophores (such as TRITC and Texas Red) emit in the red region of the spectrum ($\sim 570\text{ to }620\text{ nm}$), matching (I).
• Fluorescein (FITC) emits in the visible green region ($\sim 520\text{ to }530\text{ nm}$), matching (II).
• Allophycocyanin (APC) phycobiliprotein is matched to the blue-green / far-red category in this question set, matching (III).
  Matching pairs: (A)-(IV), (B)-(I), (C)-(II), (D)-(III), which is option 4.