AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
During sudden intense activity, the muscle cells may not get enough oxygen. In the absence of oxygen, glucose is broken down anaerobically, producing lactic acid. This lactic acid accumulates in the muscle cells, causing cramps (pain and stiffness).
This question is from the chapter on Life Processes (anaerobic respiration in muscles), not directly from the provided passages on Control and Coordination. The examiner expects: (1) lack of oxygen during intense activity, (2) anaerobic breakdown of glucose producing lactic acid, and (3) lactic acid accumulation causing cramps. These three points cover both marks. Keep the answer concise and use correct terms: anaerobic respiration, lactic acid, accumulation.