Coal-fired power plants release emissions such as nitrogen compounds into the air. the nitrogen and water cycle combine when nitrogen returns to the soil as acid rain through which water cycle process? a.) precipitation b.) respiration c.) transpiration d.) nitrification

This process is called precipitation. Still, the process is formation of liquid from gas then will go down the surface.

The tricky part of this question is the combination of nitrogen and water, as this process is not nitrification. Nitrification is the conversion of ammonia to nitrous or nitric oxide by nitrifying bacteria. Transpiration if evaporation of water through plant leaves. Respiration is the conversion of oxygen to carbon dioxide by organisms.