Which of the following agents is a common precursor to acid rain?

Nitrogen oxides are a key precursor to acid rain due to their role in the formation of nitric acid in the atmosphere. When nitrogen oxides are released into the air, especially from combustion processes such as those in vehicles and power plants, they can react with water vapor, oxygen, and other compounds in the atmosphere to form nitric acid. This acid can then be deposited as precipitation, contributing to the phenomenon known as acid rain.

The impact of acid rain is significant, as it can lead to environmental issues such as soil degradation, damage to aquatic ecosystems, and harm to buildings and infrastructure. While carbon dioxide can contribute to acidification through the formation of carbonic acid, its role in acid rain is less direct. Heavy metals and urban waste do not directly contribute to the acidification of precipitation in the same way that nitrogen oxides do, thus making nitrogen oxides the most relevant precursor to acid rain among the listed options.