The correct answer is: A. Infrared radiation emitted by the earth’s surface.
A radiation inversion is a condition in which the temperature of the air increases with height. This can happen when the air near the ground is cooled by radiation from the earth’s surface, while the air higher up is warmer. This can create a layer of warm air that traps the cooler air below it, leading to a temperature inversion.
The primary cause of a radiation inversion is infrared radiation emitted by the earth’s surface. During the night, the earth’s surface cools by radiating heat into space. This heat is in the form of infrared radiation, which is a type of electromagnetic radiation with a wavelength longer than visible light. The infrared radiation emitted by the earth’s surface is absorbed by the atmosphere, which causes the air near the ground to cool.
The other options are not the primary cause of a radiation inversion. Solar radiation absorbed by the earth’s surface does not cause a radiation inversion, because the earth’s surface absorbs more solar radiation during the day than at night. Solar radiation reflected by the earth’s surface does not cause a radiation inversion, because the earth’s surface reflects less solar radiation during the night than at day. Infrared radiation absorbed by the atmosphere and clouds does not cause a radiation inversion, because the atmosphere and clouds absorb more infrared radiation during the day than at night.