• Aerodynamic Characteristics of Darrieus Wind Rotor:
• The Darrieus rotor is a vertical-axis wind turbine (VAWT) featuring curved aerofoil blades resembling an eggbeater:
• Low starting torque: Cannot self-start because at low tip-speed ratios, blade angles of attack stall relative to incoming wind.
• Self-starting: False (requires an auxiliary Savonius rotor or motor to start).
• High operating speed: Operates at high tip-speed ratios ($TSR \gt 4$).
• High aerodynamic efficiency: Can attain power coefficients ($C_p$) exceeding 0.35–0.40, approaching horizontal-axis turbines.
• Conclusion: Correct characteristics are (A), (C) and (E) only (Option 3).

Correct option: (3) (A), (C) and (E) only,

• Classification of Solar Air Collectors by Absorber Plate:
• Solar flat-plate air heaters are classified by their absorber surface geometry:
• Flat plate absorber: Classic smooth planar metallic sheet.
• Corrugated plate absorber: V-corrugated or sinusoidal sheet increasing heat transfer area and turbulence.
• Overlapped transparent plate absorber: Slanted staggered glass slats facilitating solar radiation penetration.
• Transpiration absorber: Porous matrix or perforated mesh through which air bleeds directly to maximize convection.
• (B) Sandwich type is a mechanical panel construction, not a standard air collector absorber surface category.
• Conclusion: (A), (C), (D) and (E) only (Option 4).

Correct option: (4) (A), (C), (D) and (E) only.

• Peak Combustion Pressure in Diesel Combustion Chambers:
• Precombustion Chambers (Indirect Injection - IDI) divide the combustion space into a small prechamber (20–40% volume) and a main chamber above the piston.
• Fuel injected into the prechamber ignites with limited oxygen, forcing rich, partially burned gases through an orifice into the main chamber, where complete burning occurs progressively.
• This two-stage progressive burning cushions the pressure rise and produces the lowest peak cylinder pressure and lowest rate of pressure rise compared to open (direct injection) chambers.
• Conclusion: Peak pressure is lowest for Precombustion chamber (Option 2).

Correct option: (2) Precombustion chamber