• Groundwater Wells and Drilling Technologies:
• Percussion (cable tool) drilling $\to$ (II): Uses heavy drill bits lifted and dropped repeatedly, exceptionally suited for hard, fractured, consolidated formations (rock/boulders).
• Rotary drilling $\to$ (I): Uses a rotating bit with circulated drilling mud (bentonite), fast and optimal for unconsolidated formations (sands, silts, clays).
• Artesian well $\to$ (IV): Taps a confined aquifer under hydrostatic piezometric pressure higher than the top of the aquifer (or ground surface).
• Perched aquifer $\to$ (III): A local lens of groundwater resting on an impermeable stratum above the regional main water table, behaving as a localized unconfined aquifer.
• Matching Result: (A) - (II), (B) - (I), (C) - (IV), (D) - (III) (Option 3).

Correct option: (3) (A) - (II), (B) - (I), (C) - (IV), (D) - (ttl)

• Biochemical Oxygen Demand (BOD) Indicator:
• Definition: Biochemical Oxygen Demand (BOD$_5$) is the empirical measurement of the mass of dissolved oxygen consumed by aerobic microorganisms at $20^\circ\text{C}$ over 5 days to decompose biodegradable carbonaceous compounds.
• Indication: Elevated BOD directly indicates high concentrations of biodegradable organic matter (sugars, proteins, lipids, starches) in agricultural, municipal, and agro-processing wastewaters.
• Conclusion: Organic matter (Option 1).

Correct option: (1) Organic matter