Assertion (A) Analysis:

• Assertion (A) states that during continued muscular activity, glycogen breaks down in the presence of oxygen, releasing energy along with metabolites like lactic acid, CO2, heat, and moisture.
• Glycogen breakdown (glycogenolysis) is a primary source of glucose for muscle cells during exercise.
• In the presence of oxygen (aerobic conditions), glucose metabolism yields significant energy (ATP), CO2, water (contributing to heat and moisture).
• While CO2, heat, and moisture are products of aerobic metabolism, lactic acid is typically associated with anaerobic metabolism (when oxygen supply is insufficient for demand).
• However, in intense or prolonged activity, both aerobic and anaerobic pathways can operate simultaneously or sequentially. Therefore, the assertion that lactic acid is released, alongside aerobic products, might be considered true in a broader context of sustained muscular effort where oxygen availability can fluctuate relative to demand.

Reason (R) Analysis:

• Reason (R) claims that oxygen restricts energy release after some time because muscles manage metabolites.
• This statement is factually incorrect. Oxygen is essential for efficient energy (ATP) production through aerobic respiration. It facilitates, rather than restricts, energy release.
• A lack of oxygen limits energy production, leading to increased reliance on anaerobic pathways and subsequent fatigue, but oxygen itself does not restrict the process. The management of metabolites is a result of metabolic activity, not a cause for oxygen restriction.
• Therefore, Reason (R) is false.

Conclusion:

• Based on the analysis, Assertion (A) is considered true in the context of sustained muscular activity involving mixed metabolic states, while Reason (R) is false.
• This corresponds to Option A.