The correct answer is D. All of the above.
Orchard heaters, wind machines, and irrigation can all be used to protect an orchard from damaging low temperatures during a radiation inversion.
Orchard heaters are used to raise the temperature of the air around the orchard. This can help to prevent the fruit from freezing. Wind machines are used to break up the inversion layer, which can allow warmer air from above to reach the orchard. Irrigation can also help to break up the inversion layer, and it can also provide a layer of insulation for the fruit.
Radiation inversion is a meteorological phenomenon that occurs when the temperature of the air near the ground decreases with height. This can happen on clear nights, when the ground loses heat to space more quickly than the air above it. The inversion layer can trap cold air near the ground, which can damage plants and crops.
Orchard heaters, wind machines, and irrigation are all effective methods of protecting orchards from radiation inversion. Orchard heaters are the most common method, but wind machines and irrigation can also be effective. The best method to use will depend on the specific orchard and the severity of the inversion.