Water conservation is not limited to conserving the amount of water available, but also considers the quality of the water available. The United States has come a long way in this area when compared to other countries. Which of the statements below is a water quality conservation method used in the United States?

A) sewage treatment plants
B) allowing runoff of irrigation water
C) throwing out old motor oil instead of recycling it
D) painting boats in or over the water instead of in dry docks