What does the Clean Water Act (CWA) define as a man-made alteration of the integrity of water?

The Clean Water Act (CWA) focuses on maintaining and restoring the integrity of the nation's waters, including lakes, rivers, and streams. In this context, the act specifically addresses how human activities can alter the natural state of water systems. By referring to "man-made alteration of the integrity of water," the CWA highlights the importance of protecting aquatic environments from pollution and degradation caused by human interventions.

The choice of water as the correct answer emphasizes that the CWA's primary goal is to ensure that water resources remain clean and untainted due to human activities. This includes the management of pollutants and the enforcement of standards to minimize any detrimental impacts on water quality. The other options—air, soil, and biological systems—although they may also be influenced by human activities, do not directly correspond to the core focus of the CWA, which specifically targets the preservation of water integrity.