AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
Acid rain lowers the pH of river water, making it too acidic for aquatic organisms to survive, thus harming or killing aquatic life.
The source passages mention that living beings carry out metabolic activities within an optimal pH range (Chapter 2) and that human activities impact the environment (Chapter 13). Acid rain disrupts the pH of water bodies, directly threatening aquatic organisms. For a 1-mark answer, state the cause (lowered pH) and its effect (harm to aquatic life) concisely in one line.