Which situation is likely to produce acid precipitation?

Heavy industrial emissions combined with humidity are likely to produce acid precipitation due to the presence of sulfur dioxide (SO2) and nitrogen oxides (NOx) released from industrial processes. When these gases are emitted into the atmosphere, they can undergo chemical reactions with water vapor, forming sulfuric acid and nitric acid. This process is enhanced in humid conditions, as the moisture in the air allows for more efficient reactions to occur. Eventually, the acids can be deposited back to the Earth's surface in the form of acid rain, which can have detrimental effects on ecosystems, water quality, and infrastructure.

In contrast, the other situations presented do not support the formation of acid precipitation. Natural forest fires typically produce smoke and particulate matter but are not a significant source of the sulfur dioxide or nitrogen oxides that contribute to acid rain. Clear, sunny weather is less conducive to the reactions that produce acid since there is less moisture in the air. Additionally, low pollution areas with grassy plains lack the industrial emissions necessary for the formation of the acidic compounds associated with acid precipitation.