Agroup of mice becomes separated by the formation of a river. over time, the northern mice became smaller and whiter, while the southern mice became larger and browner. this is an example of:

sulfur dioxide

explanation: acid rain is caused by a chemical reaction that begins when compounds like sulfur dioxide and nitrogen oxides are released into the air. these substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as acid rain.