Van Deemter equation for chromatographic plate height ($H$):

• $A$ represents Eddy diffusion (multiple flow paths in packed column).
• $B$ represents Longitudinal molecular diffusion of analyte.
• $C$ represents Mass transfer resistance coefficient between stationary and mobile phases.
• $u$ represents the linear mobile phase flow velocity (flow rate).
  Because all four factors (A, B, C, D) are explicitly present in the equation, Option 3 is correct.

Subcellular compartmentalization of photorespiratory enzymes across the three organelles:

• Glycolate oxidase oxidizes glycolate to glyoxylate in the Peroxisome -> (II).
• Glycine decarboxylase complex converts two glycine molecules to serine, $\text{CO}_2$, and $\text{NH}_3$ in the Mitochondria -> (I).
• Glycerate kinase phosphorylates D-glycerate to 3-phosphoglycerate in the Chloroplast stroma -> (IV).
• NADPH-dependent hydroxypyruvate reductase 2 (HPR2) provides a cytosolic bypass for reduction of hydroxypyruvate to glycerate in the Cytosol -> (III).

Hydrogen bonding geometry in beta-pleated sheets:
Assertion (A) is true: Parallel β-sheets are inherently less stable than antiparallel β-sheets.
Reason (R) is true: In antiparallel β-sheets, the interstrand hydrogen bonds are planar, linear ($180^\circ$), and perpendicular to the polypeptide backbone, providing optimal orbital overlap and maximal strength. In contrast, in parallel β-sheets, the hydrogen bonds run at skewed, non-linear angles, resulting in distorted and weaker hydrogen bonding.
Because this bond distortion directly explains the reduced stability, (R) is the correct explanation of (A).