• Recession Limb Characteristics of a Unit Hydrograph:
• Extent of recession limb: Extends from the point of inflection on the falling side of the crest segment down to the commencement of baseflow groundwater recession. (Correct)
• Maximum basin storage: The inflection point at the top of the recession limb marks the cessation of effective rainfall inflow; storage within the watershed is at its maximum and the recession represents pure drainage of stored surface and subsurface detention. (Correct)
• (C) Concentration curve: The rising limb is called the concentration curve, not the recession limb. (Incorrect)
• (D) Dependency: The recession limb is predominantly independent of rainfall storm characteristics, depending almost exclusively on physical basin geometry and channel storage parameters. (Incorrect)
• Conclusion: (A) and (B) only (Option 4).

Correct option: (4) (A) and (B) only.

• NRCS-SCS Hydrologic Soil Groups (HSG) Classification:
• In the SCS Curve Number method, soils are categorized into four hydrologic groups based on minimum infiltration capacity and runoff potential:
• Group A (Low runoff potential): Deep sands, gravels with high infiltration rates ($\gt 7.6\text{ mm/h}$) and rapid water transmission.
• Group B (Moderately low runoff potential): Moderately deep to deep sandy loams and loams with moderate infiltration ($3.8 - 7.6\text{ mm/h}$).
• Group C (Moderately high runoff potential): Soils with low infiltration rates ($1.3 - 3.8\text{ mm/h}$) having shallow layers impeding downward drainage, clay loams, and shallow sandy clays.
• Group D (High runoff potential): Heavy clay soils with high swelling potential, claypans, and high water tables ($\lt 1.3\text{ mm/h}$).
• Conclusion: Group C represents Moderately high runoff potential (Option 3).

Correct option: (3) Moderately high runoff potential