A meteorological station at an altitude of 500 m records a temperature of 20°C. Using the environmental lapse rate of 6.5°C per 1000 m, what would be the expected temperature at sea level?

Using the environmental lapse rate of 6.5°C per 1000 m, the temperature decrease over 500 m = (6.5 × 500)/1000 = 3.25°C. Since temperature increases as altitude decreases, the sea-level temperature = 20°C + 3.25°C = 23.25°C. Option C incorrectly adds the full 6.5°C, and option A subtracts instead of adding.