The primary cause of the change in water quality in Flint, Michigan, was B. The city was taken off the Detroit water system to save money.
In April 2014, Flint switched its water source from Lake Huron (provided by Detroit) to the Flint River during a period of financial crisis. The river water was not properly treated with corrosion inhibitors, which led to the leaching of lead from aging pipes into the drinking water, resulting in a public health crisis. While the contamination of the water is linked to the decision to change the water source, the failure to adequately treat the water was a significant factor in the resulting lead contamination.