The correct answer is A. At sunset.
A radiation temperature inversion is a layer of the atmosphere where the temperature increases with height. This can happen when the sun is low in the sky, such as at sunrise or sunset. The sun’s rays are less direct at these times, so they do not heat the ground as much. This causes the air near the ground to be cooler than the air above it.
Option B is incorrect because near sunrise, the sun is low in the sky and the air is cooler. Option C is incorrect because toward the end of the morning, the sun is higher in the sky and the air is warmer. Option D is incorrect because between 2 and 5 pm, the sun is highest in the sky and the air is warmest.