• Assertion (A) is True: Advection fog forms when a warm, moist air mass moves horizontally over a colder land or water surface, cooling the bottom layer below its dew point temperature.
• Reason (R) is True: Radiation fog develops under calm, clear nocturnal skies due to radiational cooling of the ground surface.
• Relationship: Both statements are factually correct meteorological descriptions of distinct fog mechanisms, but Reason (R) describes radiation fog and does not explain the physical mechanism of advection fog.
• Conclusion: Both (A) and (R) are correct but (R) is NOT the correct explanation of (A) (Option 2).

Correct option: (2) Both (A) and (R) are true but (R) is NOT the correct explanation of (A).

• Assertion (A) is Correct: Windbreaks and shelterbelts create a sheltered leeward zone where wind speed is significantly attenuated (typically over a distance of $15-25$ times tree height), reducing aerodynamic turbulence and crop evapotranspiration.
• Reason (R) is Correct: Sensible and latent heat transfer away from the crop canopy depends directly on turbulent aerodynamic diffusion driven by wind velocity ($E \propto u(e_s - e_a)$); reduction in wind speed dampens turbulent vapor transport.
• Relationship: Because wind speed reduction diminishes turbulent atmospheric vapor transport, Reason (R) directly explains Assertion (A).
• Conclusion: Both (A) and (R) are correct and (R) is the correct explanation of (A) (Option 1).